CVE-2022-33994 in Gutenberg Plugin
Summary
by MITRE • 07/31/2022
The Gutenberg plugin through 13.7.3 for WordPress allows stored XSS by the Contributor role via an SVG document to the "Insert from URL" feature. NOTE: the XSS payload does not execute in the context of the WordPress instance's domain; however, analogous attempts by low-privileged users to reference SVG documents are blocked by some similar products, and this behavioral difference might have security relevance to some WordPress site administrators.
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Analysis
by VulDB Data Team • 08/29/2022
The vulnerability CVE-2022-33994 represents a stored cross-site scripting flaw within the Gutenberg plugin for WordPress, affecting versions through 13.7.3. This security issue specifically targets users with the Contributor role, who can potentially inject malicious scripts into the WordPress environment through the "Insert from URL" feature. The vulnerability occurs when a Contributor uploads or references an SVG document that contains malicious JavaScript code, which then gets stored within the WordPress database and executed whenever the content is rendered. The flaw is particularly concerning because it allows low-privileged users to bypass normal security restrictions and execute arbitrary code in the context of other users' browsers, creating a significant vector for attacks that could compromise user sessions or steal sensitive information.
The technical nature of this vulnerability stems from insufficient input validation and sanitization within the Gutenberg plugin's handling of SVG files. When users with Contributor privileges attempt to insert content from external URLs, the plugin fails to properly sanitize SVG documents, allowing potentially malicious code to persist in the system. The XSS payload executes in the browser context of the WordPress site but operates outside the WordPress instance's domain, which creates a unique security landscape where traditional domain-based security controls may not fully protect against the attack. This behavior differs from similar security products that block such attempts, making it potentially more dangerous for WordPress administrators who might not expect this specific vulnerability to exist. The vulnerability is categorized under CWE-79 as Cross-Site Scripting, and it aligns with ATT&CK technique T1566.001 for Phishing with Malicious Attachments, as it enables attackers to craft malicious content that can be delivered to unsuspecting users.
The operational impact of this vulnerability extends beyond simple script execution, as it can be leveraged to perform session hijacking, data exfiltration, or redirect users to malicious sites. Attackers with Contributor access could craft SVG files that contain tracking code or malicious payloads that execute when other users view posts containing the compromised content. The stored nature of the vulnerability means that even if the initial upload occurs during a brief period when security controls are less strict, the malicious content remains persistent and continues to pose a threat. This vulnerability particularly affects WordPress sites that allow Contributors to upload content, which is common in multi-author environments where content moderation is managed through role-based access controls. The security implications are compounded by the fact that many WordPress administrators might not consider Contributor-level users as potential threat actors, making this vulnerability particularly insidious and difficult to detect in properly configured systems.
Mitigation strategies for CVE-2022-33994 should include immediate patching of the Gutenberg plugin to version 13.7.4 or later, which addresses the specific SVG sanitization issue. Administrators should also implement additional security measures such as restricting the types of files that Contributors can upload, implementing more robust content filtering, and monitoring for unusual file uploads. Network-level controls can be deployed to block external SVG references or to scan uploaded content for known malicious patterns. Regular security audits should be conducted to ensure that all WordPress plugins and themes are up to date, as this vulnerability demonstrates how seemingly minor flaws in content management systems can create significant security risks. The vulnerability also underscores the importance of least privilege principles in WordPress environments, where Contributor roles should not be granted the ability to insert content from external sources without proper sanitization controls. Organizations should also consider implementing web application firewalls that can detect and block malicious SVG content, and establish clear policies regarding contributor access to content insertion features that could potentially be exploited for XSS attacks.