CVE-2009-3266 in Web Browser
Summary
by MITRE
Opera before 10.01 does not properly restrict HTML in a (1) RSS or (2) Atom feed, which allows remote attackers to conduct cross-site scripting (XSS) attacks, and conduct cross-zone scripting attacks involving the Feed Subscription Page to read feeds or create feed subscriptions, via a crafted feed, related to the rendering of the application/rss+xml content type as "scripted content."
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Analysis
by VulDB Data Team • 08/22/2021
The vulnerability described in CVE-2009-3266 represents a critical cross-site scripting flaw in Opera web browsers prior to version 10.01. This security weakness specifically targets the browser's handling of RSS and Atom feed content, creating an environment where malicious actors can inject arbitrary scripts into feed readers. The vulnerability stems from Opera's insufficient validation and sanitization of HTML content within these feed formats, allowing attackers to craft malicious feeds that exploit the browser's rendering engine when processing application/rss+xml content types.
The technical implementation of this vulnerability occurs through the improper handling of scripted content within feed subscription pages. When Opera processes RSS or Atom feeds, it fails to adequately filter or escape HTML elements that might contain malicious script code. This flaw operates at the intersection of content rendering and security boundaries, particularly affecting the feed subscription functionality where users interact with external content. The vulnerability is classified under CWE-79 as Cross-Site Scripting, specifically manifesting as a weakness in input validation and output encoding. Attackers can leverage this flaw by creating malicious feeds containing embedded JavaScript or other malicious code that executes in the context of the user's browser session.
The operational impact of this vulnerability extends beyond simple XSS attacks to encompass cross-zone scripting capabilities that can bypass traditional security boundaries. Users who subscribe to or read feeds through the affected Opera versions become vulnerable to attacks that can execute code in the context of the feed subscription page, potentially allowing attackers to steal session cookies, modify browser behavior, or access sensitive user data. The attack vector is particularly concerning because it operates through legitimate feed subscription mechanisms, making it difficult for users to distinguish between safe and malicious feeds. This vulnerability directly relates to ATT&CK technique T1212 - Exploitation for Credential Access, as it can be used to harvest user credentials or session information through malicious feed content.
The security implications of CVE-2009-3266 demonstrate the importance of proper content validation in web applications, particularly those that handle external data feeds or user-generated content. The flaw highlights the need for robust input sanitization and output encoding practices when processing structured data formats like RSS and Atom feeds. Organizations using Opera browsers prior to version 10.01 should implement immediate mitigations including browser updates, feed validation mechanisms, and user education regarding the risks of subscribing to untrusted feeds. The vulnerability also underscores the necessity of maintaining up-to-date security practices and the importance of regular browser updates to protect against known exploitation vectors. Additionally, web developers should consider implementing Content Security Policy headers and other defensive measures to limit the impact of similar vulnerabilities in their applications.
This vulnerability serves as a reminder of how seemingly innocuous features like feed subscription can become attack vectors when proper security controls are not implemented. The flaw demonstrates the critical importance of maintaining security boundaries even in application areas that might not be considered primary attack surfaces. The remediation approach requires both immediate patching of the affected browser versions and long-term implementation of comprehensive content validation strategies. Security professionals should monitor for similar patterns in other applications that handle external structured data, as the underlying principles of this vulnerability apply broadly to any system processing untrusted content through web-based interfaces. The incident emphasizes the need for continuous security assessment and the implementation of defense-in-depth strategies that protect against exploitation through multiple attack vectors.