A Bug's Life: Analyzing the Lifecycle and Mitigation Process of Content Security Policy Bugs

The constantly evolving Web exerts a chronic pressure on the development and maintenance of the Content Security Policy (CSP), which stands as one of the primary security policies to mitigate attacks such as cross-site scripting. Indeed, to attain comprehensiveness, the policy must account for virtually every newly introduced browser feature, and every existing browser feature must be scrutinized upon extension of CSP functionality. Unfortunately, this undertaking's complexity has already led to critical implementational shortcomings, resulting in the security subversion of all CSP-employing websites.

In this paper, we present the first systematic analysis of CSP bug lifecycles, shedding new light on bug root causes. As such, we leverage our automated framework, BugHog, to evaluate the reproducibility of publicly disclosed bug proofs of concept in over 100,000 browser revisions. By considering the entire source code revision history since the introduction of CSP for Chromium and Firefox, we identified 123 unique introducing and fixing revisions for 75 CSP bugs. Our analysis shows that inconsistent handling of bugs led to the early public disclosure of three, and that the lifetime of several others could have been considerably decreased through adequate bug sharing between vendors. Finally, we propose solutions to improve current bug handling and response practices.