CVE-2017-7798 in Firefox
Summary
by MITRE
The Developer Tools feature suffers from a XUL injection vulnerability due to improper sanitization of the web page source code. In the worst case, this could allow arbitrary code execution when opening a malicious page with the style editor tool. This vulnerability affects Firefox ESR < 52.3 and Firefox < 55.
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Analysis
by VulDB Data Team • 11/26/2025
The vulnerability identified as CVE-2017-7798 represents a critical cross-user interface language xul injection flaw within Firefox's developer tools functionality. This issue stems from inadequate sanitization mechanisms applied to web page source code when processed through the style editor tool, creating a pathway for malicious actors to exploit the browser's internal architecture. The vulnerability specifically targets the Firefox Extended Support Release version 52.2 and earlier, as well as standard Firefox versions prior to 55, making a substantial portion of the browser user base susceptible to this attack vector.
The technical exploitation of this vulnerability occurs through the manipulation of XUL markup within web pages that are subsequently processed by Firefox's developer tools. XUL injection allows attackers to inject malicious XUL elements into the browser's user interface, potentially bypassing standard security boundaries that separate web content from browser internals. When a user opens a malicious page containing crafted XUL code within the style editor tool, the improperly sanitized input can execute arbitrary code with the privileges of the browser process. This represents a severe privilege escalation vulnerability that can enable full system compromise through carefully crafted web content.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with the ability to manipulate browser internals and potentially access sensitive user data. The attack requires user interaction through opening a malicious page, but once executed, the attacker can leverage the developer tools environment to perform actions such as reading local files, modifying browser behavior, or even installing persistent malware. This vulnerability aligns with CWE-79 Cross-site Scripting and CWE-94 Code Injection, as it combines user interface manipulation with code execution capabilities, making it particularly dangerous in the context of browser security.
Mitigation strategies for this vulnerability primarily involve updating to affected versions of Firefox that contain the necessary sanitization patches. Users should immediately upgrade to Firefox ESR 52.3 or later, and Firefox 55 or higher to eliminate exposure to this attack vector. Organizations should implement security awareness training to prevent users from visiting untrusted websites that may contain malicious XUL content. Additionally, browser hardening measures such as disabling developer tools in production environments where possible, and implementing web content filtering solutions that can detect and block suspicious XUL injection attempts, provide additional layers of protection against this vulnerability. The ATT&CK framework categorizes this vulnerability under T1059 Command and Scripting Interpreter and T1071 Application Layer Protocol, as it leverages browser scripting capabilities to execute malicious code through legitimate developer tools functionality.