CVE-2018-6944 in UltimateMember Plugin
Summary
by MITRE
core/lib/upload/um-file-upload.php in the UltimateMember plugin 2.0 for WordPress has a cross-site scripting vulnerability because it fails to properly sanitize user input passed to the $temp variable.
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Analysis
by VulDB Data Team • 02/08/2023
The CVE-2018-6944 vulnerability resides within the UltimateMember plugin version 2.0 for WordPress, specifically in the core/lib/upload/um-file-upload.php file. This security flaw represents a classic cross-site scripting vulnerability that emerges from inadequate input sanitization practices. The vulnerability manifests when user-provided data is improperly handled and subsequently reflected back to users without proper sanitization measures. The $temp variable serves as the conduit through which malicious input can be injected and executed within the context of a victim's browser session. This particular implementation fails to apply appropriate output encoding or validation mechanisms that would normally prevent malicious scripts from being stored and subsequently executed.
The technical exploitation of this vulnerability follows established patterns for reflected XSS attacks where an attacker can craft malicious input that gets processed and stored within the application's temporary storage mechanisms. When the $temp variable contains unsanitized user data, any subsequent retrieval or display operation can execute malicious JavaScript code within the browser context of authenticated users. This vulnerability operates under the CWE-79 principle of inadequate input validation and falls squarely within the ATT&CK framework's T1203 technique for Exploitation for Client Execution. The flaw represents a critical oversight in the plugin's data handling procedures where user input should undergo rigorous sanitization before being processed or stored.
The operational impact of this vulnerability extends beyond simple data corruption or display issues. An attacker who successfully exploits this vulnerability can execute arbitrary JavaScript code in the browser of any user who views the affected content or interacts with the compromised upload functionality. This could lead to session hijacking, credential theft, redirection to malicious sites, or the execution of additional malicious payloads. The vulnerability affects WordPress installations using the UltimateMember plugin, making it particularly concerning given the widespread adoption of this popular user management solution. Attackers can leverage this vulnerability to gain persistent access to user sessions, potentially compromising entire user bases that rely on the plugin for membership and user management functions.
Mitigation strategies for CVE-2018-6944 require immediate attention from WordPress administrators and security teams. The primary recommendation involves upgrading to a patched version of the UltimateMember plugin where proper input sanitization has been implemented for the $temp variable handling. Organizations should also implement additional defensive measures including input validation at multiple layers, output encoding for all dynamic content, and regular security auditing of plugin components. Network-level protections such as web application firewalls can provide additional defense in depth, though they should not replace proper code-level fixes. Security teams should conduct comprehensive vulnerability assessments to identify other potential similar flaws within the WordPress ecosystem and ensure that all user-supplied data undergoes appropriate sanitization before processing or storage. The vulnerability underscores the critical importance of proper input validation and output encoding practices in preventing cross-site scripting attacks, aligning with industry best practices outlined in OWASP Top 10 and similar security frameworks.