Senior Offensive Security Engineer

Senior Offensive Security Engineer

Cardiff, London or Remote (UK)

We're on a mission to make money work for everyone.

We're waving goodbye to the complicated and confusing ways of traditional banking.

After starting as a prepaid card, our product offering has grown a lot in the last 10 years in the UK. As well as personal and business bank accounts, we offer joint accounts, accounts for 16-17 year olds, a free kids account and credit cards in the UK, with more exciting things to come beyond. Our UK customers can also save, invest and combine their pensions with us.

With our hot coral cards and get-paid-early feature, combined with financial education on social media and our award winning customer service, we have a long history of creating magical moments for our customers!

We're not about selling products - we want to solve problems and change lives through Monzo

London/Cardiff/UK Remote | £76,500 - £90,000 + Incentive awards tied to your performance + Benefits

Our Offensive Security team

You'll be joining Monzo's Offensive Security team, part of our wider Security collective. We're a team of curious, hands on security professionals who think like attackers to help keep Monzo and our customers safe. We work across everything from customer facing products and mobile apps to cloud infrastructure, internal systems, and emerging technologies like AI.

Our role is to find weaknesses before others do. Through security testing, red and purple teaming, and adversarial research, we uncover vulnerabilities, demonstrate real-world impact, and help teams build more secure systems. We work closely with engineers and security partners across Monzo, bringing an attacker mindset into the room and helping shape security decisions through collaboration, curiosity, and practical expertise.

You'll play a key role by...

• Leading offensive security projects from initial idea through to execution and reporting
• Simulating real world attacks to uncover vulnerabilities across our systems, infrastructure, and products
• Partnering with engineering and security teams to improve detection, response, and resilience
• Bringing an attacker mindset into conversations - asking "what if?" and challenging assumptions
• Producing proof-of-concept exploits to clearly demonstrate risk and drive meaningful fixes
• Mentoring others in the team and acting as a highly independent technical lead on complex engagements

We'd love to hear from you if…

• You have a strong attacker mindset and are naturally curious about how systems can be broken
• You've got hands on experience in offensive security across areas like web, mobile, cloud, or infrastructure
• You're comfortable working across modern tech stacks (e.g. Kubernetes, AWS/GCP, microservices) or excited to learn
• You can take ownership of ambiguous problems and drive them through to impactful outcomes
• You enjoy collaborating with others and influencing teams to think more securely
• You're experienced in security testing and/or have relevant certifications (e.g. OSCP, CREST)

Not ticking every box? That's totally okay! Studies show that women and people of colour might hesitate to apply unless they meet every single requirement. At Monzo, we're dedicated to creating a diverse and welcoming team. If you're passionate about this role and keen to learn and grow with us, we encourage you to apply— even if you don't have everything that's listed just yet. Drop us your application, we'd love to hear from you!

What's in it for you

£76,500 - £90,000 Incentive awards tied to your performance This role can be based in our London office, but we're open to distributed working within the UK (with ad hoc meetings in London) ⏰ We offer flexible working hours and trust you to work enough hours to do your job well, and at times that suit you and your team. £1,000 learning budget each year to use on books, training courses and conferences. We will set you up to work from home; all employees are given Macbooks and for fully remote workers we will provide extra support for your work-from-home setup. Plus lots more! Read our full list of benefits.

The application journey has 3 key steps

• 30 min recruiter call
• 30 min call with the hiring manager
• 2 hours of technical and behavioural interviews

This process should take around 3-4 weeks - your schedule is really important to us, so we promise to be as flexible as possible!

Equal opportunities for everyone

Diversity and inclusion are a priority for us and we're making sure we have lots of support for all of our people to grow at Monzo. At Monzo, we're embracing diversity by fostering an inclusive environment for all people to do the best work of their lives with us. This is integral to our mission of making money work for everyone. You can read more in our blog, 2026 Diversity and Inclusion Report and 2025 Gender Pay Gap Report.

We're an equal opportunity employer. All applicants will be considered for employment without attention to age, ethnicity, religion, sex, sexual orientation, gender identity, family or parental status, national origin, or veteran, neurodiversity or disability status.

If you have a preferred name, please use it to apply. We don't need full or birth names at application stage