CVE-2018-6943 in UltimateMember Plugin
Summary
by MITRE
core/lib/upload/um-image-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 vulnerability identified as CVE-2018-6943 resides within the UltimateMember plugin version 2.0 for WordPress, specifically in the file core/lib/upload/um-image-upload.php. This issue represents a classic cross-site scripting vulnerability that arises from insufficient sanitization of user input. The flaw manifests when the plugin processes image uploads and fails to properly sanitize data passed to the $temp variable, creating an avenue for malicious actors to inject malicious scripts into the application's execution flow.
The technical nature of this vulnerability aligns with CWE-79, which defines cross-site scripting as a security weakness that allows attackers to inject client-side scripts into web applications. The vulnerability occurs because the plugin does not adequately validate or sanitize the $temp variable, which likely contains user-provided data during the image upload process. When users upload images, the plugin processes metadata and file information that gets stored in this variable without proper sanitization, enabling attackers to embed malicious JavaScript code that can execute in the context of other users' browsers.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to perform various malicious activities including session hijacking, credential theft, and data exfiltration. An attacker could craft specially formatted image files or manipulate upload parameters to inject scripts that would execute when other users view the uploaded content or interact with the plugin's functionality. This vulnerability particularly affects WordPress installations using the UltimateMember plugin, where user-generated content handling creates multiple potential attack vectors through the image upload mechanism.
The exploitation of this vulnerability requires an attacker to have access to the plugin's upload functionality, typically through a user account with appropriate permissions or by leveraging other vulnerabilities to gain access. According to ATT&CK framework, this vulnerability maps to T1059.007 for script injection techniques and T1566 for social engineering through malicious file uploads. The attack surface is particularly concerning in multi-user environments where administrators or regular users might unknowingly trigger the execution of malicious code through legitimate plugin usage patterns.
Mitigation strategies for CVE-2018-6943 should include immediate patching of the UltimateMember plugin to version 2.1.0 or later, which contains the necessary sanitization fixes. Organizations should also implement additional security measures such as input validation at multiple layers, content security policies to restrict script execution, and regular security audits of plugin installations. Network segmentation and monitoring of file upload activities can help detect anomalous behavior that might indicate exploitation attempts. The vulnerability highlights the importance of proper input sanitization in web applications and demonstrates how seemingly innocuous functionality like image uploads can become security risk vectors when proper validation is omitted.