CVE-2026-119521 in Paid Member Subscriptions Plugin
Summary
by MITRE • 11/03/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Cozmoslabs Paid Member Subscriptions paid-member-subscriptions allows Stored XSS.This issue affects Paid Member Subscriptions: from n/a through 3.1.3.
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Analysis
by VulDB Data Team • 11/03/2026
The identified security flaw represents a classic instance of Improper Neutralization of Input During Web Page Generation, commonly known as Cross-Site Scripting or XSS. Specifically, this vulnerability manifests as a Stored XSS within the Cozmoslabs Paid Member Subscriptions plugin for WordPress, affecting versions ranging from n/a through 3.1.3. Unlike reflected XSS attacks where malicious scripts are executed via manipulated URLs, stored vulnerabilities persist on the target server because user-supplied input is saved in a database or other persistent storage mechanism without adequate sanitization. When this tainted data is subsequently retrieved and rendered to users by the web application, it executes arbitrary JavaScript code within the context of the victim's browser session. This specific implementation flaw allows an attacker to inject malicious scripts that remain active until manually removed from the system, creating a long-term threat vector against any user who views the compromised content.
From a technical perspective, the root cause lies in insufficient input validation and output encoding mechanisms during the web page generation process. The plugin likely accepts untrusted data through administrative interfaces or public-facing forms related to subscription management, payment details, or user profiles, and stores this data directly into the database without applying necessary escaping functions such as wp_kses_post or similar sanitization routines appropriate for WordPress development standards. When the application later generates pages containing these stored values, it fails to encode special characters like angle brackets, quotes, and ampersands that have syntactic meaning in HTML and JavaScript. Consequently, the browser interprets the injected script tags not as plain text but as executable code, allowing the attacker's payload to run with the same privileges and context as legitimate application scripts.
The operational impact of this vulnerability is severe due to its persistent nature and potential for widespread exploitation. An attacker can craft a malicious payload that steals session cookies, hijacks administrative sessions, or performs actions on behalf of authenticated users without their knowledge. In the context of a subscription management plugin, which often handles sensitive financial data and user credentials, successful exploitation could lead to unauthorized access to premium features, manipulation of billing information, or complete compromise of the underlying WordPress installation if combined with other vulnerabilities. Furthermore, because the script is stored on the server, it can be delivered to multiple victims automatically as they visit affected pages, facilitating large-scale phishing campaigns or malware distribution under the guise of a trusted domain. This significantly increases the blast radius compared to one-time reflected attacks and complicates remediation efforts since every instance of the vulnerable content must be identified and cleaned from the database.
Industry standards classify this vulnerability under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'). The specific subtype here is Stored XSS, which aligns with MITRE ATT&CK technique T1059.007 (JavaScript) within the Execution and Persistence tactics. Attackers leverage this capability to establish a foothold in the network environment by compromising user sessions or installing web shells if server-side execution vectors are also present. The persistence aspect of stored XSS allows attackers to maintain access over time, making it particularly dangerous for applications handling sensitive business logic like payment processing and membership management.
Mitigation strategies must address both immediate remediation and long-term defensive posture improvements. For organizations running affected versions of Paid Member Subscriptions, the primary action is to upgrade immediately to version 3.1.4 or later where this vulnerability has been patched by Cozmoslabs. If upgrading is not immediately feasible, administrators should manually audit database entries for suspicious script tags in fields associated with user input and remove them. Additionally, implementing a Web Application Firewall can provide an additional layer of defense by filtering out malicious payloads before they reach the application logic or are rendered to users. From a development standpoint, adhering to secure coding practices is essential; this includes enforcing strict allow-list validation for all inputs, applying context-aware output encoding based on where data will be displayed (HTML body, attribute, JavaScript, etc.), and utilizing Content Security Policy headers to restrict the sources from which scripts can execute. Regular security audits and penetration testing should also be conducted to identify similar flaws in other plugins or custom code within the WordPress ecosystem.