CVE-2024-5639 is an authorization bypass vulnerability classified under CWE-639 (Authorization Bypass Through User-Controlled Key) affecting the User Profile Picture plugin developed by cozmoslabs for WordPress. The vulnerability exists in all versions up to and including 2.6.1 within the 'rest_api_change_profile_image' REST API endpoint. This endpoint fails to properly validate a user-controlled key parameter, allowing authenticated users with Author-level access or higher to update the profile picture of any other user on the WordPress site. The root cause is an Insecure Direct Object Reference (IDOR), where the plugin does not verify that the user making the request is authorized to modify the targeted user's profile image. The vulnerability can be exploited remotely over the network without requiring user interaction beyond authentication. The CVSS v3.1 base score is 4.3 (medium), reflecting low complexity and no impact on confidentiality or availability, but a partial impact on integrity. No patches or official fixes are currently linked, and no known exploits in the wild have been reported. This flaw could be used to deface user profiles, potentially facilitating phishing or social engineering attacks by impersonating users or damaging reputations. The vulnerability highlights the importance of strict authorization checks on user-controlled parameters in REST API endpoints, especially in multi-user content management systems like WordPress.

The primary impact of CVE-2024-5639 is the unauthorized modification of user profile pictures by authenticated users with Author-level privileges or higher. While this does not expose sensitive data or disrupt service availability, it compromises the integrity of user profiles. Attackers could exploit this to impersonate other users visually, potentially misleading site visitors or administrators. This could facilitate social engineering, phishing, or reputational damage within organizations relying on WordPress for internal or external communications. In environments where user identity and trust are critical, such as corporate intranets, educational institutions, or membership sites, this vulnerability could undermine user confidence and lead to broader security concerns. Although the vulnerability requires authentication, many WordPress sites have multiple users with elevated privileges, increasing the risk. The lack of known exploits reduces immediate threat but does not eliminate the risk of future weaponization. Organizations worldwide using the affected plugin version are at risk of unauthorized profile tampering, which could be leveraged as part of larger attack campaigns or insider threats.

To mitigate CVE-2024-5639, organizations should first verify if they are using the cozmoslabs User Profile Picture plugin version 2.6.1 or earlier. If so, immediate steps include: 1) Restricting Author-level and higher privileges to trusted users only, minimizing the attack surface. 2) Monitoring and auditing profile picture changes for unusual activity or unauthorized modifications. 3) Applying any available patches or updates from the vendor as soon as they are released. Since no official patch is currently linked, consider temporarily disabling the plugin or restricting access to the vulnerable REST API endpoint via web application firewall (WAF) rules or custom code to enforce authorization checks. 4) Implementing additional server-side validation to ensure that users can only modify their own profile pictures, possibly through custom plugin modifications or hooks. 5) Educating administrators and users about the risk of profile impersonation and encouraging vigilance against suspicious profile changes. 6) Regularly reviewing user roles and permissions to ensure least privilege principles are enforced. These targeted mitigations go beyond generic advice by focusing on access control tightening, monitoring, and compensating controls until an official patch is available.