Senior Software Engineer; Security

Timezone preference: GMT-5 through GMT+1 Summary

The Wikimedia Foundation is looking for a Senior Software Engineer to join the Product Safety and Integrity team and build new security features to protect Wikipedia and our other projects. This is a very hands‑on engineering role, working alongside a team of engineers and product managers to design and implement new features to protect and reassure our users and to ensure the platform remains resilient against attacks.

You are a seasoned software engineer with experience building security features in large‑scale systems. You understand the importance of testing and documentation, and common pitfalls in developing secure web applications. You have a passion for the WMF mission. We operate in a highly transparent manner, and the work we do touches thousands of editors every day.

You will be working primarily on our Media Wiki platform which powers Wikipedia. As a top 10 website, we must meet stringent performance standards while addressing new security challenges such as supporting modern authentication technologies, detecting and preventing platform abuse from bots, and planning and rolling out improvements to our security architecture by defending against emerging security threats.

• Helping design, develop, and deliver security features, with safety and security in mind
• Working with other engineering teams to ensure that they make safe architectural and implementation choices
• Leading by example in code review, decision‑making, and team culture — fostering transparency, empathy, and collaboration
• Developing, reviewing, and deploying security features developed by the Foundation and community members
• Performing security maintenance and addressing technical debt in security‑critical components
• Providing support for application security incidents and operations

We value the right mindset and potential over a checklist of specific experiences, and these are the traits we’ve identified that make great additions to our team so far.

• 5+ years of experience as a software engineer, ideally with focus on security
• Ability to work effectively in a modern PHP and JavaScript codebase
• Driving technical quality and operational excellence by defining and reinforcing standards in testing, observability, and system reliability;
• Comfortably and autonomously creating proofs of concept, writing design documents, and breaking down complex projects into actionable tasks to support less experienced team members
• Experience in developing secure software or security‑related product features
• A strong interest in working with a talented security team and learning more specialist security skills such as exploiting and mitigating application‑level vulnerabilities
• Ability to explain complex security issues and their implications on privacy and risk to non‑technical audiences
• Sensitivity to the security challenges faced by participants in a large, international project
• Experience working in a remote, distributed team

• Experience working on anti‑abuse mechanisms such as CAPTCHA and bot detection
• Previous experience building security countermeasures against attacks on technologies at the web, backend, and database level
• Experience finding and fixing security bugs and reviewing code for security gaps
• A working knowledge of threat modeling and secure design patterns
• Prior experience with Media Wiki or Wikimedia projects
• Contributions to open‑source software

The Wikimedia Foundation is the nonprofit organization that operates Wikipedia and the other Wikimedia free knowledge projects. Our vision is a world in which every single human can freely share in the sum of all knowledge. We believe that everyone has the potential to contribute something to our shared knowledge, and that everyone should be able to access that knowledge freely.

We host Wikipedia and the Wikimedia projects, build software experiences for reading, contributing, and sharing Wikimedia content, support the volunteer communities and partners who make Wikimedia possible, and advocate for policies that enable Wikimedia and free knowledge…