Overview
A high-severity Stored Cross-Site Scripting (XSS) vulnerability has been identified in the Simple User Registration plugin for WordPress, tracked as CVE-2025-12160. This vulnerability affects all versions up to, and including, 6.6 of the plugin. Due to insufficient input sanitization and output escaping of the ‘wpr_admin_msg’ parameter, unauthenticated attackers can inject malicious JavaScript code into the WordPress database. This code will then execute whenever a user accesses a page where the ‘wpr_admin_msg’ is displayed, potentially leading to account compromise, data theft, or other malicious activities.
Technical Details
The vulnerability lies in the lack of proper input sanitization and output escaping for the ‘wpr_admin_msg’ parameter. An unauthenticated attacker can inject arbitrary HTML and JavaScript code through this parameter. This injected code is then stored in the WordPress database without proper validation. When the ‘wpr_admin_msg’ is rendered on a page (likely in an administrative interface or a user-facing notification), the injected JavaScript executes within the user’s browser. The absence of sanitization before storage and escaping before output allows the injected script to bypass security measures and compromise the affected user’s session.
CVSS Analysis
This vulnerability has been assigned a CVSS score of 7.2, indicating a HIGH severity. The CVSS vector string is likely something along the lines of:
AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Where:
- AV:N (Attack Vector: Network) – The vulnerability is exploitable over a network.
- AC:L (Attack Complexity: Low) – Exploiting the vulnerability requires no special access conditions or extenuating circumstances.
- PR:N (Privileges Required: None) – No privileges are required to exploit the vulnerability.
- UI:R (User Interaction: Required) – User interaction is required to exploit the vulnerability. In this case, a user must access a page where the injected script is rendered.
- S:C (Scope: Changed) – An exploited vulnerability can affect resources beyond the attacker’s authority or privileges.
- C:L (Confidentiality: Low) – There is limited impact on confidentiality.
- I:L (Integrity: Low) – There is limited impact on integrity.
- A:N (Availability: None) – There is no impact on availability.
This high severity score is primarily due to the vulnerability being remotely exploitable without authentication and the potential for an attacker to execute arbitrary code in the context of another user’s session.
Possible Impact
Successful exploitation of this vulnerability can have significant consequences, including:
- Account Compromise: Attackers can steal user session cookies, allowing them to impersonate legitimate users and gain unauthorized access to their accounts.
- Data Theft: Attackers can inject code to steal sensitive information such as personal details, financial data, or other confidential information displayed on the affected page.
- Malicious Redirects: Attackers can redirect users to phishing sites or other malicious websites.
- Defacement: Attackers could modify the content of the website, leading to defacement.
- Privilege Escalation: In certain scenarios, attackers may be able to leverage the XSS vulnerability to gain higher privileges within the WordPress installation.
Mitigation or Patch Steps
The recommended mitigation steps are as follows:
- Update the Simple User Registration plugin: Immediately update the plugin to the latest version, which includes a fix for this vulnerability. Contact the plugin developer if a patched version isn’t available yet.
- Disable the Plugin: If an update is not immediately available, temporarily disable the Simple User Registration plugin until a patched version is released.
- Web Application Firewall (WAF): Implement a WAF with rules designed to block XSS attacks. Configure the WAF to specifically filter input to the ‘wpr_admin_msg’ parameter.
- Monitor for Suspicious Activity: Closely monitor your WordPress website for any unusual activity, such as unauthorized logins, changes to user profiles, or suspicious database modifications.
References
WordPress Plugins Trac – Changeset
Wordfence Threat Intelligence
CVE-2025-12160 at MITRE
