CVE-2018-20153 in WordPress
Summary
by MITRE
In WordPress versions before 5.0.1, contributors could modify new comments made by users with greater privileges, possibly causing XSS.
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Analysis
by VulDB Data Team • 06/19/2023
This vulnerability exists in WordPress versions prior to 5.0.1 and represents a significant access control flaw that allows contributors to manipulate comments created by users with higher privileges. The issue stems from insufficient authorization checks within the comment management system where contributors can modify comments regardless of the original commenter's role or permissions. This represents a clear violation of the principle of least privilege and demonstrates inadequate input validation and access control mechanisms. The vulnerability is categorized under CWE-284 which specifically addresses improper access control, and aligns with ATT&CK technique T1078 which covers valid accounts and privilege escalation through unauthorized access to system resources.
The technical implementation of this flaw occurs when a contributor attempts to edit a comment that was originally posted by an administrator or editor. The WordPress comment editing functionality fails to properly verify whether the current user has sufficient privileges to modify the target comment. This allows unauthorized modifications to potentially malicious content or sensitive information that was originally posted by higher-privileged users. The vulnerability creates a pathway for cross-site scripting attacks because contributors can inject malicious scripts into comments that may be executed when other users view those comments. The flaw specifically impacts the comment editing endpoint where the system does not properly enforce role-based access controls.
The operational impact of this vulnerability is substantial as it enables a low-privilege user to compromise the integrity of content created by high-privilege users. This creates a potential vector for persistent XSS attacks where malicious scripts can be embedded into comments and executed whenever other users view the affected content. The vulnerability also undermines the trust model within WordPress installations, as it allows unauthorized modifications to content that should remain protected. Attackers could exploit this to inject malicious code that could steal cookies, redirect users to malicious sites, or perform other malicious activities. The risk is particularly elevated in multi-user environments where contributors might have access to sensitive information or internal communications.
Mitigation strategies should begin with immediate upgrade to WordPress version 5.0.1 or later where this vulnerability has been addressed through proper access control enforcement. Organizations should implement additional monitoring of comment modifications to detect unauthorized changes to privileged content. Security configurations should include regular review of user roles and permissions to ensure contributors only have access to appropriate functionality. Network-level protections such as content security policies can help mitigate the impact of potential XSS attacks. The fix implemented in WordPress 5.0.1 specifically addresses the authorization check by ensuring that users can only modify comments they have created or have explicit permission to edit, thereby resolving the CWE-284 access control issue. Regular security audits and penetration testing should be conducted to identify similar authorization flaws in custom plugins or themes that might be vulnerable to similar attacks.