This bypass technique involves leveraging Content-Security-Policy Templates (CSPTs), which are often underrated in security circles, to circumvent Web Application Firewalls (WAFs). By exploiting quirks in frontend frameworks, attackers can bypass protections implemented by WAFs and other intermediary layers like CDNs and Server-Side Rendering (SSR) systems. Complex systems composed of WAFs, CDNs, and SSR can have parser differentials—the differences in how each component parses and interprets requests. Attackers exploit these parser differentials along with framework-specific quirks to successfully perform attacks that leak authorization headers, expose Personally Identifiable Information (PII), and achieve Cross-Site Scripting (XSS) and CSS Injection. This method is particularly effective because it leverages the subtleties of how various layers process incoming requests, allowing attackers to bypass traditional security filters. Understanding and mitigating these bypass paths requires a deep understanding of parsers and frontend framework behaviors as well as robust WAF configurations that account for complex attack vectors involving multiple layers.
For more insights, check out the original tweet here: https://twitter.com/busf4ctor/status/1955272181874565608. And don’t forget to follow @busf4ctor for more exciting updates in the world of cybersecurity.