CVE-2025-9633 Overview
The LH Signing plugin for WordPress contains a Cross-Site Request Forgery (CSRF) vulnerability affecting all versions up to and including 2.83. The flaw exists in the plugin_options function, which lacks proper nonce validation. Unauthenticated attackers can modify plugin settings by tricking an authenticated administrator into clicking a crafted link or visiting a malicious page. This vulnerability is tracked as [CWE-352] and requires user interaction to succeed. The issue was reported through Wordfence's threat intelligence program and disclosed publicly in September 2025.
Critical Impact
Attackers can silently alter LH Signing plugin configuration on any WordPress site running version 2.83 or earlier by luring an administrator to a malicious URL, potentially undermining document signing workflows.
Affected Products
- LH Signing plugin for WordPress — all versions up to and including 2.83
- WordPress sites with an authenticated administrator session active
- Deployments relying on LH Signing for document signing configuration
Discovery Timeline
- 2025-09-11 - CVE-2025-9633 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-9633
Vulnerability Analysis
The vulnerability is a classic Cross-Site Request Forgery [CWE-352] affecting the plugin's settings handler. The plugin_options function processes administrative configuration changes without verifying a WordPress nonce token. Because WordPress relies on nonces to confirm that state-changing requests originated from a legitimate admin session, missing validation allows any cross-origin request to succeed if it carries the administrator's authentication cookies.
An attacker does not need credentials or a prior foothold on the target site. The exploit requires only that a logged-in administrator visits an attacker-controlled page or clicks a malicious link. The browser automatically attaches the administrator's session cookies to the forged POST request, and the plugin accepts the parameters as legitimate. Integrity impact is limited to plugin settings rather than full site compromise, but altered configuration can affect signing behavior and downstream document integrity workflows.
Root Cause
The root cause is missing or incorrect nonce validation in the plugin_options function within lh-signing.php. The settings form referenced in partials/option-settings.php does not enforce a check_admin_referer() or wp_verify_nonce() call before applying submitted values. Reference the plugin source at line 1870 and line 1886 for the affected handler.
Attack Vector
The attack is network-based and requires user interaction. An attacker hosts a page containing a hidden form or image tag that submits a POST request to the vulnerable WordPress endpoint. When an authenticated administrator loads the malicious page, the browser submits the request with valid session cookies, and the plugin updates its options without further verification. See the Wordfence advisory for additional context.
Detection Methods for CVE-2025-9633
Indicators of Compromise
- Unexpected changes to LH Signing plugin settings recorded in the WordPress options table without a corresponding admin action log entry.
- HTTP referer headers on plugin settings POST requests pointing to external, untrusted domains.
- Administrator sessions submitting settings updates immediately after visiting external links or email attachments.
Detection Strategies
- Enable WordPress activity logging plugins to capture administrator actions with timestamps and originating IP addresses.
- Alert on POST requests to LH Signing settings endpoints that lack a same-origin referer or WordPress nonce parameter.
- Correlate web server access logs with admin session activity to identify cross-origin form submissions.
Monitoring Recommendations
- Monitor the wp_options table for unauthorized modifications to LH Signing-related keys.
- Track outbound clicks from administrator email accounts and flag suspicious URLs targeting the WordPress admin path.
- Review web application firewall logs for POST requests to /wp-admin/ endpoints missing the _wpnonce parameter.
How to Mitigate CVE-2025-9633
Immediate Actions Required
- Update the LH Signing plugin to a version newer than 2.83 once the vendor releases a patched build.
- If no patch is available, deactivate and remove the LH Signing plugin until a fixed version ships.
- Instruct administrators to log out of WordPress before browsing untrusted sites or clicking unsolicited links.
Patch Information
At the time of NVD publication, no fixed version was listed. Monitor the Wordfence vulnerability record and the WordPress plugin repository for an updated release addressing the missing nonce validation in plugin_options.
Workarounds
- Deploy a web application firewall rule that blocks POST requests to LH Signing settings endpoints when the _wpnonce parameter is absent.
- Enforce SameSite=Strict cookie attributes on WordPress authentication cookies to reduce cross-origin cookie submission.
- Require administrators to use a dedicated browser profile for WordPress administration, isolated from general web browsing.
- Restrict /wp-admin/ access by source IP address using server-level controls where feasible.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
