CVE-2022-50955: WordPress Curtain Plugin CSRF Vulnerability

CVE-2022-50955 Overview

CVE-2022-50955 is a Cross-Site Request Forgery (CSRF) vulnerability in the WordPress Curtain plugin version 1.0.2. The plugin manages site maintenance mode functionality but fails to validate request nonces on its administrative settings endpoint. Attackers can craft malicious requests that, when triggered by an authenticated administrator, toggle the maintenance mode state on the target site. The flaw is classified under CWE-352: Cross-Site Request Forgery. Exploitation requires social engineering to lure a logged-in administrator to a malicious page or link.

Critical Impact

Successful exploitation allows remote attackers to activate or deactivate site maintenance mode without administrator consent, disrupting site availability for legitimate visitors.

Affected Products

• WordPress Curtain Plugin version 1.0.2
• WordPress installations with the Curtain plugin enabled
• Sites where administrators are authenticated during browsing sessions

Discovery Timeline

• 2026-05-10 - CVE-2022-50955 published to NVD
• 2026-05-12 - Last updated in NVD database

Technical Details for CVE-2022-50955

Vulnerability Analysis

The Curtain plugin exposes maintenance mode controls through the WordPress options-general.php administrative interface. The handler that processes curtain parameters does not verify a WordPress nonce token before applying state changes. Without nonce verification, the server cannot confirm that the request originated from an intentional administrator action within the WordPress dashboard.

An attacker who knows the parameter structure can host an HTML page containing an auto-submitting form or image tag that targets the vulnerable endpoint. When an authenticated administrator visits the attacker-controlled page, the browser automatically attaches valid session cookies to the cross-origin request. The plugin then accepts and processes the forged request as legitimate.

The vulnerability has limited scope because it only affects the maintenance mode toggle. It does not enable code execution, data exfiltration, or account takeover. However, repeated toggling can interrupt site operations and degrade user trust.

Root Cause

The root cause is the absence of CSRF token validation in the plugin's settings handler. WordPress provides the wp_nonce_field() and check_admin_referer() APIs for exactly this purpose, but the Curtain 1.0.2 codebase omits these protections on the maintenance mode controls.

Attack Vector

Exploitation requires an authenticated WordPress administrator with the Curtain plugin installed to visit an attacker-controlled URL or open a crafted email. The attacker crafts an HTML page that submits a POST or GET request to options-general.php with the curtain parameter set to enable or disable maintenance mode. No direct credentials are needed because the victim's authenticated session cookie authorizes the request.

Technical details and a proof of concept are available in Exploit-DB #50842 and the VulnCheck Advisory on Curtain CSRF.

Detection Methods for CVE-2022-50955

Indicators of Compromise

• Unexpected toggling of WordPress site maintenance mode without corresponding administrator activity in audit logs
• HTTP requests to /wp-admin/options-general.php containing curtain parameters with Referer headers from external domains
• Maintenance mode state changes occurring outside scheduled maintenance windows

Detection Strategies

• Monitor WordPress access logs for POST or GET requests to options-general.php where the Referer header is missing or points to an untrusted origin
• Enable WordPress audit logging plugins to record all administrative option changes with associated user, IP, and timestamp
• Inspect browser-originated requests for cross-origin patterns targeting plugin settings endpoints

Monitoring Recommendations

• Configure web application firewall rules to flag requests that modify plugin settings without same-origin Referer headers
• Alert on changes to the Curtain plugin's stored options in the WordPress wp_options table
• Track administrator session activity and correlate with external link clicks reported in email security gateways

How to Mitigate CVE-2022-50955

Immediate Actions Required

• Deactivate the Curtain plugin version 1.0.2 until a patched release is verified through the official WordPress plugin page
• Restrict access to /wp-admin/ paths by IP allowlisting where operationally feasible
• Educate administrators to log out of WordPress sessions before browsing untrusted sites or clicking external links

Patch Information

No vendor-confirmed patched version is referenced in the available advisory data. Administrators should review the WordPress Plugin Curtain page for updated releases and replace version 1.0.2 with any later release that explicitly documents CSRF protection. If no fixed version is available, remove the plugin and use an alternative maintenance mode solution that implements nonce verification.

Workarounds

• Deploy a web application firewall rule that enforces same-origin Referer checks on requests to options-general.php
• Replace the Curtain plugin with a maintained alternative that uses check_admin_referer() for state-changing operations
• Require administrators to use a dedicated browser profile or session for WordPress administration to limit cross-site exposure

# Example ModSecurity rule to block cross-origin requests to the vulnerable endpoint
SecRule REQUEST_URI "@contains /wp-admin/options-general.php" \
    "chain,deny,status:403,id:1009551,msg:'Possible CSRF against Curtain plugin'"
SecRule ARGS_NAMES "@rx ^curtain" "chain"
SecRule REQUEST_HEADERS:Referer "!@beginsWith https://your-site.example.com"