SecAppDev 2025 lecture details

Breaking and securing OAuth 2.0 in frontends

Using OAuth 2.0 in the frontend increases your attack surface. Learn why BFF is safer and how to defend against real-world token attacks.

Schedule TBD
Abstract

Everyone agrees that Cross-Site Scripting (XSS) is a real threat to browser-based applications, yet many underestimate its true power. The common practice of making a JavaScript frontend an OAuth 2.0 client, using techniques like refresh token rotation, fails to account for real-world attacker scenarios.

This talk demonstrates concrete attacks that bypass frontend token protections entirely. You'll learn why this pattern is risky and how a Backend-For-Frontend (BFF), as defined in the "OAuth 2.0 for Browser-based Apps" spec (co-authored by the speaker), offers a more secure approach.

Key takeaway

Frontend OAuth 2.0 patterns, even with token protections, leave apps exposed—real security comes from moving sensitive logic to a secure backend.

Content level

Deep-dive

Target audience

Anyone involved in building and securing web frontends

Prerequisites

None

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Philippe De Ryck
Philippe De Ryck

Security Expert, Pragmatic Web Security

Expertise: Web security, API security, OAuth 2.0, OpenID Connect

More details

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