CVE-2026-6399 Overview
The General Options plugin for WordPress contains a stored cross-site scripting (XSS) vulnerability in versions up to and including 1.1.0. The flaw exists in the Contact Number field (ad_contact_number), where the plugin uses sanitize_text_field() for output escaping. This function strips HTML tags but does not encode double-quote characters, allowing attackers to break out of HTML attribute context. Authenticated attackers with Administrator-level access can inject arbitrary JavaScript into the admin settings page. The injected payload executes whenever any administrator visits the General Options settings page, creating an admin-to-admin script injection vector [CWE-79].
Critical Impact
Authenticated administrators can inject persistent JavaScript that executes in other administrators' browser sessions on the WordPress admin settings page.
Affected Products
- WordPress General Options plugin versions up to and including 1.1.0
- All WordPress installations running the vulnerable plugin
- Multi-administrator WordPress environments are at higher risk of cross-account script execution
Discovery Timeline
- 2026-05-20 - CVE-2026-6399 published to NVD
- 2026-05-20 - Last updated in NVD database
Technical Details for CVE-2026-6399
Vulnerability Analysis
The vulnerability stems from incorrect output escaping in the plugin's admin settings template. The plugin calls sanitize_text_field() on the stored ad_contact_number value before echoing it inside a double-quoted HTML attribute such as value="...". While sanitize_text_field() removes HTML tags and normalizes whitespace, it does not convert double-quote characters to ". An attacker who supplies a payload containing a raw double-quote character can terminate the attribute early and inject new attributes, including event handlers such as onmouseover or onfocus.
WordPress's wp_magic_quotes mechanism prefixes user-supplied quote characters with a backslash. However, HTML parsers do not interpret \" as an escaped quote. The backslash renders as a literal character, and the bare double-quote still closes the attribute. The plugin should use esc_attr() instead of sanitize_text_field() for attribute-context output, since esc_attr() properly encodes double-quote characters.
Root Cause
The root cause is a context-mismatched escaping function. sanitize_text_field() is an input sanitization helper, not a context-aware output escaper. Using it to render values inside an HTML attribute leaves double-quote characters unencoded and breaks the attribute boundary.
Attack Vector
Exploitation requires Administrator-level privileges, which limits the population of potential attackers. An attacker submits a crafted Contact Number value containing a double-quote followed by injected attributes such as onmouseover="alert(1)". The payload persists in the plugin's stored options. When any administrator subsequently loads the General Options settings page, the malicious attribute executes in their browser. See the Wordfence Vulnerability Analysis and the WordPress Plugin Source for technical details.
Detection Methods for CVE-2026-6399
Indicators of Compromise
- Unexpected JavaScript, event handlers, or stray quote characters present in the ad_contact_number option stored in the wp_options table
- Administrator browser sessions executing unfamiliar scripts when visiting the General Options settings page
- New or unexpected administrator accounts created shortly after settings page visits
Detection Strategies
- Query the WordPress database for the plugin's stored options and inspect the Contact Number value for ", <script, onerror=, or onmouseover= substrings
- Review WordPress audit logs for changes to General Options plugin settings by administrator accounts
- Inspect outbound HTTP traffic from administrator browsers loading /wp-admin/ for unexpected external script requests or beacon callbacks
Monitoring Recommendations
- Enable a WordPress activity logging plugin to track option updates and administrator session activity
- Monitor for anomalous DOM events or script execution on /wp-admin/admin.php pages associated with the General Options plugin
- Alert on creation of new administrator accounts, REST API token generation, or modification of user roles following plugin option changes
How to Mitigate CVE-2026-6399
Immediate Actions Required
- Update the General Options plugin to a version above 1.1.0 once the vendor releases a patched release
- If no patched version is available, deactivate and remove the General Options plugin until a fix ships
- Audit the stored value of ad_contact_number and remove any payloads containing quotes, angle brackets, or event handler attributes
- Review administrator accounts and rotate credentials for any account that may have been compromised through script execution
Patch Information
No patched version is listed in the NVD entry at the time of publication. Monitor the WordPress.org plugin page and the Wordfence advisory for an updated release that replaces sanitize_text_field() with esc_attr() in attribute-context output.
Workarounds
- Restrict the number of accounts granted Administrator capability to reduce the attack surface
- Apply a web application firewall rule that blocks double-quote characters and event handler patterns in POST requests to the General Options admin page
- Use a Content Security Policy (CSP) header on /wp-admin/ that disallows inline event handlers and untrusted script sources
# Example CSP header to limit inline script execution in wp-admin
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'"
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
