CVE-2020-12113 in BigBlueButton
Summary
by MITRE
BigBlueButton before 2.2.4 allows XSS via closed captions because dangerouslySetInnerHTML in React is used.
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Analysis
by VulDB Data Team • 05/06/2025
The vulnerability CVE-2020-12113 affects BigBlueButton versions prior to 2.2.4 and represents a critical cross-site scripting flaw that arises from improper handling of user-provided content within the closed captions feature. This vulnerability specifically manifests when the application utilizes dangerouslySetInnerHTML in its React components to render closed caption text, creating an avenue for malicious actors to inject arbitrary JavaScript code into the application's user interface. The flaw stems from the application's failure to properly sanitize or escape user input before rendering it within the React DOM, allowing attackers to execute scripts in the context of other users' browsers.
The technical implementation of this vulnerability leverages the React framework's dangerouslySetInnerHTML attribute which bypasses React's built-in security mechanisms designed to prevent XSS attacks. When closed captions are processed and rendered using this attribute, any HTML or JavaScript content embedded within the caption text is directly inserted into the DOM without proper sanitization. This creates a persistent XSS vector where attackers can craft malicious caption content containing script tags or other malicious payloads that execute when other users view the captions. The vulnerability is particularly concerning because closed captions are often used in educational and corporate settings where users may not expect to encounter malicious code execution.
The operational impact of this vulnerability extends beyond simple script execution to potentially enable full session hijacking, data theft, and privilege escalation within the BigBlueButton environment. An attacker could exploit this vulnerability to steal user sessions, access confidential meeting content, or manipulate the application's functionality. The attack surface is particularly broad since closed captions are commonly used in various contexts including online education platforms, corporate meetings, and webinars where multiple users interact with the same application instance. The vulnerability affects all users who can access or view closed captions, making it a significant risk for organizations that rely heavily on real-time collaboration tools.
Mitigation strategies for CVE-2020-12113 should focus on implementing proper input sanitization and output encoding mechanisms within the application's closed caption processing pipeline. Organizations should immediately upgrade to BigBlueButton version 2.2.4 or later, which includes patches addressing the dangerouslySetInnerHTML usage. Security teams should implement Content Security Policy headers to limit script execution and employ proper HTML sanitization libraries to filter user input before rendering. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws, and maps to ATT&CK technique T1059.001 for command and scripting interpreter usage. Additionally, implementing a web application firewall rule to detect and block suspicious script patterns in caption content can provide additional protection layers against exploitation attempts.