CVE-2016-5262 in Firefox
Summary
by MITRE
Mozilla Firefox before 48.0 and Firefox ESR 45.x before 45.3 process JavaScript event-handler attributes of a MARQUEE element within a sandboxed IFRAME element that lacks the sandbox="allow-scripts" attribute value, which makes it easier for remote attackers to conduct cross-site scripting (XSS) attacks via a crafted web site.
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Analysis
by VulDB Data Team • 09/09/2022
This vulnerability exists in Mozilla Firefox versions prior to 48.0 and Firefox ESR 45.x versions prior to 45.3, representing a significant sandbox bypass issue that undermines the security model designed to isolate potentially malicious content. The flaw specifically affects the processing of JavaScript event-handler attributes within MARQUEE elements when these elements are contained within sandboxed IFRAME elements. The MARQUEE element, while deprecated in modern web standards, remains supported for backward compatibility and continues to pose security risks due to its event handling capabilities. When a web page contains a MARQUEE element with JavaScript event handlers inside a sandboxed IFRAME that lacks the critical sandbox="allow-scripts" attribute, the browser fails to properly enforce the sandbox restrictions, allowing the JavaScript code to execute in the context of the parent page rather than being confined to the sandboxed environment.
The technical implementation of this vulnerability stems from Firefox's insufficient validation of event handlers within deprecated HTML elements when they exist in sandboxed contexts. The sandbox attribute is designed to provide a security boundary that prevents scripts from executing, but the flaw allows JavaScript event handlers within MARQUEE elements to bypass these restrictions through improper attribute processing. This behavior creates a pathway for attackers to inject malicious JavaScript code that can execute with the privileges of the parent page, effectively circumventing the security protections intended by the sandbox mechanism. The vulnerability is particularly concerning because it leverages the interaction between deprecated HTML elements and modern security features, exploiting a gap in Firefox's security model that existed between the browser versions mentioned in the CVE.
The operational impact of this vulnerability is substantial as it enables remote attackers to conduct cross-site scripting attacks with minimal user interaction requirements. Attackers can craft malicious websites that embed MARQUEE elements within sandboxed IFRAMEs, allowing them to execute arbitrary JavaScript code that can steal session cookies, redirect users to malicious sites, or perform other malicious actions within the context of the victim's browsing session. The vulnerability is particularly dangerous because it can be exploited without requiring user interaction beyond visiting a malicious website, making it a prime target for drive-by download attacks and other automated exploitation techniques. The attack vector is simplified by the fact that the sandboxed IFRAME does not require explicit permission to execute scripts, yet the MARQUEE element's event handlers can still execute in the parent context, creating a security boundary violation that directly impacts user security and privacy.
Organizations and users should immediately upgrade to Firefox versions 48.0 or later for regular releases and Firefox ESR 45.3 or later for extended support releases to mitigate this vulnerability. System administrators should also implement additional monitoring for suspicious web content and ensure that web applications properly validate and sanitize user input to prevent exploitation. The vulnerability aligns with CWE-693, which covers protection mechanism failures, and maps to ATT&CK technique T1059.007 for JavaScript execution, highlighting the need for comprehensive security measures beyond simple browser updates. Security teams should also consider implementing Content Security Policy headers to add additional layers of protection against similar vulnerabilities, as this issue demonstrates the importance of robust security boundaries in web browsers and the potential for legacy HTML features to create unexpected security risks in modern web environments.