Senior Application Security Engineer

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Senior Application Security Engineer, London

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Client:

ProtonMail

Location:

London, United Kingdom

Job Category:

Other

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EU work permit required:

Yes

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Job Reference:

21d7510336c0

Job Views:

9

Posted:

22.06.2025

Expiry Date:

06.08.2025

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Job Description:

A better internet, where privacy is the default, is possible. Building this better internet might seem daunting or even unthinkable, but at Proton, this is what we do every day.

Proton was founded in 2014 by a group of scientists who met at the European Organization for Nuclear Research (CERN). Our first product,Proton Mail , is now the world’s largest encrypted email service. Subsequent Proton products, such asProton VPN ,Proton Calendar , Proton Drive and Proton Pass give our users full control over how and with whom their data is shared.

Today, Proton makes privacy universally accessible. Journalists from outlets likeThe GuardianandThe New York Times, some of the world’s largest organizations, and people in more than 180 countries have signed up for over 100 million accounts. Our diverse and dynamic team is made up of more than 400 members representing over 40 different nationalities. While we are based in Geneva, Switzerland, we have offices in Zurich, Prague, London, Vilnius, Skopje, Taipei, Paris, Barcelona and many more employees working remotely around the world.

Join one of Europe’s fastest-growing companies to help us solve challenging problems and build new products that will reach hundreds of millions of people. We want to create more than just one of the world’s most impactful tech companies; we want to create a new internet that serves the interests of all people. We need you, your voice, your ideas, and your ambition to make it happen.

The Team:

The Security team is tasked with protecting Proton’s and its users against various cyber-security threats. We ensure the confidentiality, availability and integrity of thousands of assets, necessary to the fulfillment of Proton’s privacy mission. Since 2018, the team has been providing services to other business units, including security monitoring, risk management, internal advisory, product security, vulnerability management and identity & access management.Our mandate includes the protection of people, devices, applications, infrastructure, data, software and our products. We work mainly with on-prem infrastructure and open source tools.

The security team is small yet mighty. We are a close-knit group of people who work hard to help Proton achieve its mission. We strongly believe that we cannot protect our users\’ privacy if we do not protect the company\’s security.

Tech Stack and Tools:

• Proton currently offers the following products: Mail, Calendar, VPN, Pass, Drive, each of which is available on multiple platforms, including Windows, MacOS, iOS and Linux.
• Our infrastructure is entirely composed of Linux machines.
• Wherever we can, we make use of open-source technologies.

About the role:

You will be leading our efforts to ensure that Proton\’s applications are secure

What you will be doing:

• Perform penetration tests on Proton products, both those released to the public and not
• Support bug bounty triage by reproducing submissions and assessing their potential impact
• Working with engineering teams to remediate identified bugs
• Identifying and implementing improvements in product security and secure coding
• Work with the wider Security and developer units to create security guidelines
• Demonstrate the value of an “assume breach” mentality
• Perform threat modeling and security reviews: review the design of services from a security perspective to identity vulnerabilities and weaknesses in the architecture and design

What we are looking for:

• Proven experience in organizing and executing penetration tests/red team operations
• A proactive and creative application security engineer
• A proactive and creative mindset to come up with efficient and effective ways to continuously improve the security of our products
• Expertise in threat modeling
• Experience with at least two of the following iOSAndroidWindowsMacOSLinux
• Strong skills in coding and code review for at least two of the following GoRustPython

Nice to have:

• Experience or knowledge about open source tools for application security testing
• Experience in automation
• A toolbox for application security testing
• Experience or knowledge of infrastructure penetration tests

Even if you don’t meet all the requirements listed above, but feel you could still be a great fit, please still apply.

Why should you join Proton?

• Be part of a movement – Proton is not just a product or service but a community-driven movement united by a shared vision of online freedom. Our services are open source, audited, and supported by community contributions. We give back to our community by maintaining core encryption libraries and by supporting other organizations furthering the same goals as us.Proton is free, open source, neutral, independent, and community first, while remaining financially sustainable.
• Work with smart and dedicated people – Our team is diverse, collaborative, and tight-knit with people coming from all walks of life, including many of the world’s top academic institutions and organizations, such as MIT, Harvard, Stanford, Caltech, Cambridge, and ETH.
• Join a strong brand – Our encrypted email service – ProtonMail – has grown to be a staple of online security and privacy. Proton has been featured in multiple popular television and film productions, such as Mr. Robot, Knives Out, Sounds of Metal, and more.
• Grow with us – We’re one of Europe’s fastest-growing startups, doubling in size every year. Our growth gives you limitless career and educational opportunities as well as the opportunity to work side-by-side with many world-leading experts in their fields.
• Have your voice heard – We value your opinion and encourage you to speak up and share your ideas and thoughts. At Proton, no problem is someone else’s problem. We collectively strive to do the right thing and be the undisputed best in the world at everything we do.
• Benefits – these vary by location and type of contract but expect support on your vacation, parental leave, refreshment if working from the office, learning and development opportunities, equity for shared success, flexible working hours and remote work, company events and team building activities.

Proton does not accept unsolicited resumes from any sources other than directly from a candidate. Proton will not pay a fee for any placement resulting from the receipt of an unsolicited offer, even in a situation when the relevant candidate is employed by Proton.

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