CVE-2017-7812 in Firefox
Summary
by MITRE
If web content on a page is dragged onto portions of the browser UI, such as the tab bar, links can be opened that otherwise would not be allowed to open. This can allow malicious web content to open a locally stored file through "file:" URLs. This vulnerability affects Firefox < 56.
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Analysis
by VulDB Data Team • 01/15/2021
This vulnerability in Firefox versions prior to 56 represents a significant security flaw in the browser's drag and drop functionality that could enable malicious web content to bypass normal security restrictions. The issue stems from insufficient validation of drag operations that allow web content to be dropped onto browser user interface elements such as the tab bar or address bar. When legitimate web content is dragged onto these UI portions, the browser fails to properly sanitize the drop target, creating an opportunity for unauthorized file access through file:// URLs.
The technical implementation of this vulnerability exploits the browser's handling of drag and drop events within the user interface context. During normal operation, Firefox should prevent web content from directly accessing local file systems through file:// URLs, as this would constitute a serious privilege escalation. However, the flaw occurs when malicious content is dragged onto browser UI elements, allowing the drop operation to trigger a file:// URL that would normally be blocked by the browser's security model. This creates a pathway for attackers to potentially access sensitive local files that should remain protected from web-based content.
The operational impact of this vulnerability extends beyond simple information disclosure, as it could enable attackers to execute arbitrary code or gain unauthorized access to local resources. An attacker could craft malicious web pages that, when visited, would allow drag and drop operations to open local files such as configuration files, credentials, or other sensitive data. The vulnerability specifically affects the browser's security boundaries, allowing malicious content to effectively bypass the sandboxing mechanisms that normally protect local file systems from web-based access. This represents a critical flaw in the browser's security architecture that could be exploited to compromise user systems.
Mitigation strategies for this vulnerability require immediate patching of affected Firefox versions to 56 or later, where the drag and drop functionality has been properly secured. Organizations should implement comprehensive browser security policies that include automatic update mechanisms and regular security assessments. The vulnerability aligns with CWE-200, which covers "Information Exposure," and CWE-732, which addresses "Incorrect Permission Assignment," as it allows unauthorized access to local resources through improper privilege handling. From an ATT&CK framework perspective, this vulnerability maps to T1059 for command and scripting interpreter usage and T1070 for indicator removal, as attackers could use this technique to access local files and potentially exfiltrate data. The fix implemented by Mozilla involved strengthening the validation of drop targets during drag operations and ensuring that only properly authorized URLs can be executed when content is dropped onto browser UI elements, thereby restoring proper security boundaries between web content and local file systems.