A vulnerability in Mozilla Firefox, Thunderbird, and SeaMonkey could allow an unauthenticated, remote attacker to conduct spoofing attacks.
The vulnerability is due to insufficient sanitization of user-supplied input by the affected software. An unauthenticated, remote attacker could exploit this vulnerability by persuading a user to navigate away from a web page with an active select drop-down menu. If successful, an attacker could position a new web page in a manner that retains the contents of the previous web page, which could be used to conduct spoofing attacks on a targeted system.
Mozilla has confirmed the vulnerability and released software updates.
Indicators of Compromise
The following Mozilla products are vulnerable:
Firefox versions prior to 25
Firefox ESR versions prior to 24.1
Thunderbird versions prior to 24.1
SeaMonkey versions prior to 2.22
The vulnerability is due to improper handling of select elements in the affected software when it processes user-supplied input. The select drop-down menu component of the affected software fails to remove arbitrary HTML content from a web page when rendered, allowing a new page to retain the content.
An unauthenticated, remote attacker could exploit this vulnerability by convincing a user to navigate away from a web page. If successful, an attacker could position a new web page in a manner that retains the contents of the previous web page, which could be used to conduct spoofing attacks on the targeted system.
This vulnerability cannot be exploited through email in Thunderbird and SeaMonkey because the products have scripting disabled; however, the vulnerability could be exploited in the browser-like context of the products.
Administrators are advised to apply the appropriate updates.
Users are advised not to open email messages from suspicious or unrecognized sources. If users cannot verify that links or attachments included in email messages are safe, they are advised not to open them.
Administrators are advised to monitor affected systems.
Mozilla has released a security advisory at the following link: MFSA-2013-94
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Cisco Multivendor Vulnerability Alerts respond to vulnerabilities identified in third-party vendors' products. These alerts contain information compiled from diverse sources and provide comprehensive technical descriptions, objective analytical assessments, workarounds and practical safeguards, and links to vendor advisories and patches.