Nickolas Bossinas, Developer in Athens, Central Athens, Greece
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Nickolas Bossinas

Verified Expert  in Engineering

WordPress Plugins Developer

Athens, Central Athens, Greece
Toptal Member Since
September 16, 2016

Over the recent years, Nickolas has been working as a technical manager for implementing IT platforms for governments and large organizations. In parallel, he has been developing WordPress plugins. He has strong leadership and management skills, deep engineering background, and know-how in designing and implementing complex IT solutions. Specializing in PHP, HTML, JavaScript, business process management systems, and Flowable, Nickolas developed the very popular WordPress File Upload plugin.


Freelance Work
WordPress, WordPress Plugins, JavaScript, PHP, React, Material UI, CSS3, HTML5...
Sorbus Advisors LLC
PHP, MySQL, JavaScript, HTML, CSS, User Experience (UX), User Interface (UI)...
Grant Thornton Greece
Jira, GitLab, Java, React, PHP, JavaScript, WordPress, Microsoft Power BI...




Preferred Environment

Subversion (SVN), Git, Jira, GitLab, IntelliJ IDEA, Visual Studio Code (VS Code)

The most amazing...

...WordPress plugin I've created is an online collaboration platform that enables many users to work on the same document at the same time.

Work Experience

Web Developer

2009 - PRESENT
Freelance Work
  • Created the entire WordPress website for the European and National (Greek) research projects, including,,,,,, and
  • Developed plugins for several purposes, including online collaboration implementing a Zoho document editor inside a WordPress website, managing DB forms on a WordPress page, and enabling website visitors to register for events.
  • Created plugins for safely injecting JavaScript code inside a WordPress page or post, managing to lock and unlock users, posting text on Twitter, and adding and managing custom post types in WordPress websites.
  • Developed a WordPress functionality, part of another plugin, that enables WordPress websites to send requests to clients using long polling, although most web servers do not support it.
  • Built WordPress File Upload, published in, enabling file uploads from posts, pages, and sidebars. It is currently the most popular in its category, with more than 800,000 downloads.
  • Created the entire open-call platforms (WordPress websites), through which companies submitted proposals for the European energy research projects INTERRFACE, OneNet, and BD4NRG.
Technologies: WordPress, WordPress Plugins, JavaScript, PHP, React, Material UI, CSS3, HTML5, SQL, MySQL, CSS, jQuery, OAuth 2, HTML, Prototyping, Web Development, Web Design, Design, User Experience (UX), User Interface (UI), Full-stack, Blender, Front-end, Vanilla JS, Content Management Systems (CMS), Architecture, Minimum Viable Product (MVP), Startups, .NET, Full-stack Development, Cloud Infrastructure, Back-end Development, Front-end Development, Security, Responsive Web Apps, Web Scraping, SVG, Responsive, Integration, API Integration, Microsoft OneDrive, Algorithms, OneDrive, OneDrive API, Back-end, API Connectors, eCommerce APIs, Cybersecurity, REST APIs, Technical Leadership, Database Architecture, Complex SQL Queries

Full-stack PHP Developer | Benchmarking Solutions

2023 - 2024
Sorbus Advisors LLC
  • Reverse-engineered the old website code, written in Node.js, in order to understand the process and formulas that it used to conduct statistical analysis and generate reports on mergers & acquisition (M&A) data stored in the database.
  • Migrated the old website into WordPress, keeping the exact user interface.
  • Corrected several bugs related to filtering and analysis of data, user login, and registration and added new features to the website.
Technologies: PHP, MySQL, JavaScript, HTML, CSS, User Experience (UX), User Interface (UI), Node.js, WordPress, DigitalOcean, WP Engine, Vercel, Algorithms, Back-end, Database Architecture, Bootstrap, Complex SQL Queries

Director of Engineering

2021 - 2023
Grant Thornton Greece
  • Performed as the company's director of engineering, assisting the company's transformation toward developing its skills and know-how in data science and software engineering.
  • Acted as a technical manager of GoBeyond, a complex business process management platform developed by GT for the Hellenic Ministry of Finance to handle funding provided to organizations in the frame of the EU's Recovery and Resilience Facility (RRF).
  • Acquired deep know-how on Flowable, an open-source business process management platform written in Java and AngularJS v1.3. Modernized Flowable to the latest UI technologies (React 17) and integrated it with Keycloak, LDAP, and other OAuth2 systems.
  • Built several extensions for Keycloak, an open-source IDM and SSO platform. Created a new registration flow involving the confirmation of mobile phones through SMS and custom email templates and integrated it with public OAuth2 Gateways.
Technologies: Jira, GitLab, Java, React, PHP, JavaScript, WordPress, Microsoft Power BI, Data Analytics, Machine Learning, Azure, Git, Microsoft 365, SQL, MySQL, CSS, jQuery, HTML5, CSS3, Microsoft Visio, C#, OAuth 2, HTML, Keycloak, IntelliJ IDEA, WordPress Plugins, Prototyping, Web Development, Web Design, Design, User Experience (UX), User Interface (UI), Business to Government (B2G), Full-stack, Python, Front-end, Vanilla JS, SCSS, Content Management Systems (CMS), Architecture, Minimum Viable Product (MVP), Project Management, Artificial Intelligence (AI), .NET, Full-stack Development, PDF, Cloud Infrastructure, Back-end Development, Front-end Development, Security, Responsive Web Apps, Data Scraping, Web Scraping, SVG, Responsive, Data Visualization, Integration, API Integration, Algorithms, Microsoft Excel, Back-end, Orchestration, API Architecture, API Connectors, Cybersecurity, REST APIs, Redux, Technical Leadership, Agile, Database Architecture, Complex SQL Queries

Defense and Security Expert

2018 - 2021
Intracom Telecom SA
  • Modified a third-party software, written in C++ and C#, which controlled an electro-optical system to integrate the system with a better controlling device, correct errors, and add more features (e.g., contrast and brightness control).
  • Acted as the technical manager for implementing the smart policing project for the Hellenic Police. This IT solution enabled police officers to perform personal inquiries on the field from their mobile phones using face, finger, or textual input.
  • Developed a desktop application in C# for the smart policing project, which assisted in the fusion of information from over 50 Hellenic Police databases into a standard representation model. The same app generated test data to mock this DBS.
  • Created more than 130 web services in PHP with test data that mocked the Hellenic Police's infrastructure, which was used by the company's development teams to develop smart policing and perform end-to-end tests.
  • Built a fully working face recognition app in Python to mock the real third-party face recognition app of smart policing that was unavailable during development. The company's development team used it to perform end-to-end integrations.
  • Constructed a fully working fingerprint recognition app in Java to mock the Hellenic Police's AFIS, which the company's development teams used to develop smart policing and perform end-to-end tests.
Technologies: Java, JavaScript, Python, Machine Learning, Swift, SOAP, REST, Facial Recognition, Image Fingerprinting, NIST, C++, C#, Microsoft 365, SQL, WordPress, CSS, HTML5, CSS3, Microsoft Visio, HTML, GitLab, IntelliJ IDEA, WordPress Plugins, Web Development, Design, User Interface (UI), Business to Government (B2G), Full-stack, Front-end, Vanilla JS, Content Management Systems (CMS), Architecture, Project Management, Artificial Intelligence (AI), .NET, Full-stack Development, Back-end Development, Front-end Development, Data Scraping, SVG, Integration, API Integration, Algorithms, Back-end, Orchestration, API Architecture, API Connectors, Cybersecurity, Flask, REST APIs, Technical Leadership, Agile, Database Architecture, Complex SQL Queries

Research Programs Manager

2014 - 2018
INTRACOM Defense Electronics
  • Involved the company in national and European research projects on telecommunications, defense and security, and aeronautics. Contributed to the preparation of OCEAN2020, a large European defense project.
  • Involved the company in the Hellenic Civil Unmanned Aerial Vehicle (HCUAV) national research project, which referred to developing a medium size unmanned aerial system for surveillance and fire protection applications.
  • Prepared the initial conceptual proposal of the European defense project LOTUS, focused on the development of an advanced unmanned aerial system consisting of a mothership and smaller carried drones for reconnaissance applications.
  • Coordinated, as a product manager, the industrialization of SKYRIDER, an unmanned aerial system that the company aimed to include in its portfolio of products.
Technologies: Aeronautics, Business Administration, Research, Telecom Equipment & Solutions, Security, Unmanned Aerial Vehicles (UAV), Blender, Design, Blender Scripting API, Architecture, Project Management, Python, Algorithms

Innovation Manager

2009 - 2013
ONEX Company
  • Involved the company in nanotechnology. Followed a business plan, prepared the group, and established Glonatech, a spin-out company manufacturing nanomaterials and semi-final products. Acted as a member of the BOD of Glonatech.
  • Involved the company in European research projects related to nanotechnology, ICT, aeronautics, and security. Led the preparation of many proposals for public tenders, some of which were granted to the company.
  • Evaluated technology opportunities and proposed where to invest as an innovation manager. Coordinated the Glonatech strategy and bridged the gap between business and science.
  • Developed software tools to assist the implementation of several projects of ONEX using mainly WordPress with custom plugins, Delphi, and C#.
Technologies: Aeronautics, Nano, Information & Communications Technology (ICT), WordPress, Prototyping, Web Development, Design, Full-stack, Content Management Systems (CMS), Architecture, Startups, Project Management, Full-stack Development, Back-end Development, Front-end Development, Data Scraping, Integration, Algorithms, Microsoft Excel, Technical Leadership, Agile

Chief Engineer

1996 - 2009
Hellenic Air Force
  • Acted as QA officer of 112 Combat Wing from 1998 to 2000. Oversaw the preparation of maintenance statistics for the whole wing, and to do this efficiently, I developed automated reports using Excel and VBScript.
  • Worked as a staff officer of Airforce Support Command from 2000 to 2004, leading the setup of technical support for a newly established state aircraft. Headed the high-level tech support of Super Puma search and rescue helicopters.
  • Acted as a head of quality assurance of the technical support of 384 VIP Transportation Squadron from 2004 to 2008, contributing to the safe operation of the aircraft.
  • Developed software tools in Delphi for analyzing engine health monitoring data for Rolls-Royce aviation engines. These tools assisted in ensuring the safe and reliable operation of the aircraft engines.
  • Built S/W tools in Delphi to perform better troubleshooting of aircraft malfunctions. Developed a device that could parse the flight data of Embraer aircraft black boxes and then visualize the flights in Microsoft Flight Simulator.
  • Acted as a chief engineer of the Hellenic government's state aircraft from 2008 to 2009.
Technologies: Aviation, Aeronautics, Software, Aerospace & Defense, Quality Assurance (QA), PDF, Microsoft Excel

WordPress File Upload | Plugin
This is a WordPress file upload plugin I developed. It enables file uploads from WordPress pages, posts, or sidebars. The plugin also contains a visual editor for easy configuration and many options to satisfy almost all users. It's one of the most popular in its category. The free version has more than 1,000,000 downloads.

This plugin has been integrated with Google Drive, Microsoft OneDrive, Dropbox, Amazon S3, Meta Messenger, FTP, sFTP, and NextGEN Gallery. It has a hook system that allows almost all features and functions to be extended or entirely redefined. This way, several other enhancements have been implemented for customers, such as integration with WooCommerce and WebDAV, file moderation, loggers, file checkers, filename modifiers, and new file viewer columns.

It provides front-end and back-end file viewers so users can view and download their files. The UI of the upload form relies on a templating system, which allows one to implement it with any technology. A new version is on its way, where the upload form is created with React and MaterialUI.

Upload of Files of Unlimited Size | Plugin
An extract of the professional version of the WordPress File Upload plugin. It contains the client-side code in JavaScript and server-side code in PHP that enable uploads of files of unlimited size from an upload form. Normally web servers impose restrictions regarding the size of uploaded content and upload duration.

Files larger than 100MB will usually fail. The attached code demonstrates how to use the JavaScript slice() function to cut the file in pieces or chunks on the client side, upload them individually, and reassemble them on the server side. This way, there are no restrictions. The WordPress File Upload plugin has been reported to succeed in uploading files of more than 4GB.

Security Features for File Uploads
The installation of a plugin in a WordPress website that adds file upload forms on the front end imposes many security risks if security measures are not taken into account seriously.

The link above is a comprehensive study about threats related to WordPress plugins and upload forms. It details these threats, their implementation process, and preventive measures. It also demonstrates in detail how the WordPress File Upload plugin addresses all these threats individually.

Filters and Actions in JavaScript
WordPress allows developers to customize its elements and add or change functionalities through filters and actions. This hook technique is used for PHP code on the server side. However, there is no such hook technique for client-side code in JavaScript. The WordPress File Upload plugin extract creates a framework that enables filters and actions to be used in JavaScript code, just like in PHP.

Drag-and-drop Functionality
A commercial version of the WordPress File Upload plugin implements a file drag-and-drop feature onto a form. Users can add multiple files to a form by selecting them from their computer and dragging them onto the upload form. This drag-and-drop functionality is implemented using JavaScript and its drag-and-drop events.

Iptanus Website
Iptanus is a portal for promoting my commercial plugins and providing technical support. The support area contains pages with instructions about published plugins. The Technical Articles area has many technical articles about various functionalities of the published plugins. There are also many articles related to general web-programming issues, like how to add Google reCAPTCHA without public and private keys and web security.

The website uses WooCommerce, which has been extended through its filtering system with a plugin to perform custom operations.

OAuth 2.0 Authentication

The aim of this project was to showcase a TweetME plugin. It contains PHP code that demonstrates OAuth 2.0 authentication process with a Twitter account so that the plugin can post tweets from that account.

Recordings from a Webcam
This is an extract of a professional version of the WordPress File Upload plugin. It contains JavaScript code that enables the recording of video and audio streams from the device's webcam and mic.

It uses the latest HTML5 technology, like the getUserMedia function, and promises to achieve it. However, it also contains fallback mechanisms for compatibility with old browsers, mobile phones, and Internet Explorer.

Google reCAPTCHA Without Keys
This article explains how to implement Google reCAPTCHA inside a WordPress plugin without keys. Usually, public and private keys are required to use Google reCAPTCHA, which are taken from the website.

When Google issued version 1, it allowed developers to issue global keys when using reCAPTCHA in their plugins. So, when these plugins were installed on users' websites, the users did not have to issue their own keys. When Google issued version 2, which is safer and easier to use, it withdrew the ability to issue global keys. Thus, this article explains how developers can implement version 2 of Google reCAPTCHA without requiring users to issue their own keys. Google reCAPTCHA without keys is an exciting yet experimental technology.

It is fully implemented in the pro version of the WordPress File Upload plugin.

Nanopolytox Website

Nonapolytox was the European Union research project that ran between 2010 to 2013 and examined the effects of nanomaterials. I developed its website using WordPress.

The website had to generate dynamic reports in Excel, Microsoft Word, and PDF on the results of the experiments conducted by the scientists. To do this, I developed a custom plugin. At that time, there were no efficient tools to generate Excel, Microsoft Word, and PDF documents with PHP. So, whenever a user requested a report, the plugin transferred the required data using REST to another Windows server. This is where a custom application I developed in Delphi received and processed data, generated a requested file, and returned it to the WordPress website. There were a lot of challenges to making this mechanism work reliably because the Windows application required a lot of time to generate the files.


DELOS was a European project that ran between 2013 and 2015 and related to developing an e-learning platform for the operation and management of biogas production units.

I developed the project's main website with WordPress and the e-learning platform with Canvas LMS, one of the most well-known LMS platforms, written with Ruby on Rails.


A European research project that ran between 2019 and 2022 aimed to develop an interface between transmission and distribution system operators and energy grids.

The project included a tendering platform so that companies and universities could submit proposals and get funding through the project to develop IT tools for energy grids.

I developed the tendering platform using WordPress, a custom theme, and a custom plugin. The tendering platform allowed applicants to register, download all necessary documents, submit their proposals, resubmit if they wanted, and download their final proposals. It also permitted admin users to control and manage applicant companies and users.

The whole platform was developed as a product to be replicated, allowing the same tendering platform to be used in European research projects ONENET and BD4NRG.

RegCom Platform

My team and I developed the RegCom platform for Grant Thornton, Greece. It is based on WordPress. I created all the main features of the platform using a custom plugin and a custom theme.

Implementing an internal search engine that would perform free-text searches in PDF documents was the most challenging part. The whole operation was done using PHP and JavaScript. No third-party online services were used. A user performs a free-text search and gets a list of matched PDF documents like Google Books search. The user sees the excerpt that contains the search keywords with the latter being highlighted.

The platform can also display the whole PDF document to the user with the search keywords highlighted in the PDF. Again, this is done entirely using PHP and JavaScript without third-party online services.

After the initial implementation of the platform, we decided to modernize the front end and experiment with a WordPress API, so we implemented the front end using React and WordPress as a back-end environment. All the exchange of information between the front and back ends was done using a WordPress REST API.

The project is still ongoing.

Smart Policing

During my occupation in Intracom Telecom SA, I took over the technical leadership of Smart Policing project.
The project was about the development of an advanced search engine for Hellenic Police, where policemen would be able to perform identification of persons, vehicles and other objects from their mobile phones, either by textual search, or fingerprint scanning or face recognition.
I led five different teams who took over the development of the various parts of the system.
The core system, the search engine, was development with Java and it was able to perform mass searches to over 50 databases of Hellenic Police, other Greek Ministries and international databases through Web Services. It was also integrated with a 3rd party face recognition system, as well as the fingerprint recognition system of Hellenic Police.
The clients, from where policemen conducted searches were mobile phones and browsers. So, native Android (Java for Android) and iOS (Swift) clients were developed, as well as a web client (React).
Besides the technical leadership, I also designed the whole system, I defined all the REST and SOAP specs of the web services and I also set up the whole test environment (a digital twin of Hellenic Police infrastructure).

GoBeyond Platform
During my occupation in Grant Thornton Greece as the Director of Engineering, I took over, as Technical Leader, the development of GoBeyond platform.
The platform was a web-based Information System, from where large enterprises could submit loan applications.
The platform was a Business Process Management (BPM) system and it was developed with Java 11 Spring Boot, using Flowable opensource. Flowable is a BPM framework developed with Java Spring Boot.
I led three different teams, who took over the development of the platform (one backend team and two frontend teams).
Besides my leadership role, I performed a lot of coding. Flowable opensource has an old frontend on AngularJS. I made the necessary modifications so that it is integrated with React. I also integrate it with Keycloak and LDAP.
This was the first time we used Flowable and there was no experience from the team. So I had to learn it, do the necessary customizations and then train my team to follow up.
In addition, I extended Keycloak through Service Provider Interfaces (SPIs) so that it can send SMS messages during user registration.
I also performed almost all devops tasks (setting of the development, testing and also production environments and CI/CD operations).

Vodafone RRF Portal
During my occupation at Grant Thornton Greece as Director of Engineering I took over as Technical Manager the development of a web-based platform for Vodafone Hellas, that would allow its customers to request coupons for digital services, in the frame of RRF (a European fund for assisting Members States to recover from COVID).
The platform was developed with Java Spring Boot using Flowable opensource. I took over almost all development, backend and frontend, due to lack of resources at that time.
I integrated Flowable with Keycloak and LDAP, as well as with external services of the Ministry of Finance. I also integrated it with Marmelab, an admin framework in NodeJS and Wordpress.
The frontend was developed with AngularJS, which I mixed with React and MaterialUI components to improve the look and feel.
I also performed all devops tasks (setup of development, UAT and production environments and all CI/CD scripts).
2011 - 2014

Master's Degree in Applied Engineering

National Technical University of Athens - Athens, Greece

2008 - 2010

Master's Degree in Business Administration

Institut Universitaire Kurt Bösch - Sion, Switzerland

1992 - 1996

Bachelor's Degree in Aeronautics

Hellenic Air Force Academy - Athens, Greece


REST APIs, Complex SQL Queries, Dropbox API, jQuery, React, OneDrive, OneDrive API, X (formerly Twitter) API, WordPress REST API, WordPress API, Google Drive API, WooCommerce API, Facebook Messenger API, TensorFlow, OpenLDAP, Blender Scripting API, Node.js


Microsoft Excel, Git, MATLAB, Blender, Keycloak, IntelliJ IDEA, Subversion (SVN), AutoCAD, Microsoft Visio, CorelDRAW, Jira, GitLab, Microsoft Power BI, Canvas LMS, VMware, Notepad++, Figma, Postman, SoapUI, NGINX


Vanilla JS, OAuth 2, Material UI, .NET, Redux, Bootstrap, Nano, Spring Boot, AngularJS, Spring Security, Flask


PHP, HTML5, SQL, CSS3, CSS, HTML, JavaScript, Delphi, C#, Java, Python, Fortran, Python 3, Swift, C++, C#.NET, Java 11, Bash Script, UML, SCSS


Responsive, Agile, API Architecture, MVC Design, Rapid Application Development (RAD), REST, Management, Computational Mechanics, Testing, DevOps, BPMN


WordPress, WordPress Theme Design, Azure, Visual Studio Code (VS Code), WooCommerce, Oracle, Docker, Windows Server 2019, Windows Server 2016, Windows Server 2010, Linux CentOS 7, Ubuntu Linux, Android, iOS, MacOS, DigitalOcean, Vercel


MySQL, Database Architecture, PostgreSQL, InterBase, Amazon S3 (AWS S3), Azure Cloud Services, WP Engine

Industry Expertise

Cybersecurity, Web Design, Project Management


WordPress Plugins, Microsoft 365, Technical Leadership, Integration, Prototyping, Web Development, Design, User Experience (UX), User Interface (UI), Business to Government (B2G), Full-stack, Content Management Systems (CMS), Architecture, Full-stack Development, Back-end Development, Front-end Development, SVG, API Integration, Algorithms, Back-end, Flowable, Machine Learning, Security, WordPress Themes, APIs, Microsoft OneDrive, Front-end, Minimum Viable Product (MVP), Startups, Artificial Intelligence (AI), PDF, Cloud Infrastructure, Responsive Web Apps, Data Scraping, Web Scraping, Orchestration, API Connectors, eCommerce APIs, SOAP, Facial Recognition, Image Fingerprinting, NIST, Data Analytics, Aeronautics, Aircraft Engineering, Materials Science, Finite Element Method (FEM), Business Administration, Innovation, Team Leadership, Engineering, Finite Element Analysis (FEA), Research, Telecom Equipment & Solutions, Unmanned Aerial Vehicles (UAV), Information & Communications Technology (ICT), Aviation, Software, Aerospace & Defense, Quality Assurance (QA), Plugins, WebDAV, FTP/S, Elementor, reCAPTCHA, Web Services, Fingerprint Readers, Technical Project Management, Enterprise Mobility Management (EMM), Convolutional Neural Networks (CNN), Generative Adversarial Networks (GANs), Search Engines, System Design, Digital Twin, CI/CD Pipelines, Ubuntu Server, Marmelab, Virtual Machines, Business Process Management (BPM), File Uploader, Ajax, Data Visualization, Materials Engineering

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