Stealth Exposures: Advanced Side-Channel Attacks Targeting Mozilla Firefox's Protocol Handlers

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Presented at M0leCon 2025 by

Satoki Tsuji

In this presentation, we examine a series of information disclosure flaws uncovered in Mozilla Firefox, with particular emphasis on how URL protocol handlers can pose security threats. Our investigation shows that attackers can leverage subtle timing variations and side channels to detect installed applications and configured URL protocols. Notably, the vulnerabilities CVE-2024-5690 and CVE-2024-9398 enable adversaries to profile user systems and gather reconnaissance data without any direct interaction from the user. This research underscores the critical need to address emerging side-channel exploits in modern browsers and offers practical guidance for developers and security professionals alike. By applying these insights, it is possible to strengthen user privacy and mitigate advanced exploitation tactics in today's threat landscape.