CVE-2018-5169 in Firefox
Summary
by MITRE
If manipulated hyperlinked text with "chrome:" URL contained in it is dragged and dropped on the "home" icon, the home page can be reset to include a normally-unlinkable chrome page as one of the home page tabs. This vulnerability affects Firefox < 60.
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Analysis
by VulDB Data Team • 02/04/2020
This vulnerability resides in the Firefox browser's handling of chrome protocol URLs during drag and drop operations, specifically when interacting with the home page icon. The flaw allows for manipulation of the browser's home page configuration through crafted hyperlinked text containing chrome: URLs. When such content is dragged and dropped onto the home icon, it can potentially inject chrome protocol pages into the user's home page tabs, effectively bypassing normal security restrictions that prevent direct access to internal browser pages. The vulnerability stems from insufficient validation and sanitization of URL protocols during drag and drop operations, particularly when these operations involve privileged chrome protocol URLs that are normally inaccessible to regular web content. This represents a privilege escalation vector where user-controlled content can manipulate browser internals.
The technical implementation of this vulnerability exploits the browser's lack of proper protocol validation during drag and drop interactions. Chrome protocol URLs typically provide access to Firefox's internal browser components such as about:config, about:home, or other administrative pages that are normally restricted from being directly accessed by web content. When the drag and drop operation occurs on the home icon, the browser fails to properly validate that the URL being added is a legitimate user-accessible URL rather than a privileged chrome protocol URL. This allows attackers to construct malicious hyperlinks containing chrome: URLs and then use the drag and drop functionality to inject these privileged URLs into the user's home page configuration, effectively creating a persistent backdoor or information disclosure mechanism.
The operational impact of this vulnerability is significant as it allows for persistent modification of the browser's home page configuration, potentially enabling attackers to create malicious home page entries that could redirect users to phishing sites or display malicious content. The vulnerability affects all Firefox versions prior to 60, representing a substantial attack surface where users are exposed to potential exploitation through social engineering or malicious web content that could trick users into dragging and dropping crafted hyperlinks. This type of vulnerability falls under the CWE-79 category for Cross-Site Scripting, specifically involving improper neutralization of user-controllable input during drag and drop operations. The attack requires user interaction through the drag and drop mechanism, making it a user-initiated privilege escalation rather than an automated exploit, but still represents a serious security risk.
Mitigation strategies for this vulnerability involve implementing proper URL protocol validation during drag and drop operations, particularly when these operations involve privileged protocol URLs such as chrome:, about:, or other internal browser protocols. Browser vendors should ensure that only user-accessible URLs are allowed to be added to home page configurations, with strict filtering of privileged protocol URLs that should remain inaccessible to regular web content. The fix implemented in Firefox 60 likely involved enhancing the validation logic to prevent chrome protocol URLs from being added to home page tabs during drag and drop operations, requiring additional checks to ensure that only standard HTTP/HTTPS URLs can be persisted in the user's home page configuration. This vulnerability also highlights the importance of input validation in all user interaction mechanisms, particularly those involving privileged operations, and aligns with ATT&CK technique T1059 for executing malicious code through browser-based attacks. Organizations should ensure their Firefox installations are updated to version 60 or later to prevent exploitation of this vulnerability, and users should be educated about the risks of dragging and dropping content from untrusted sources.