CVE-2021-24743 in Podcast Subscribe Buttons Plugin
Summary
by MITRE • 10/18/2021
The Podcast Subscribe Buttons WordPress plugin before 1.4.2 allows users with any role capable of editing or adding posts to perform stored XSS.
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Analysis
by VulDB Data Team • 10/22/2021
The vulnerability identified as CVE-2021-24743 affects the Podcast Subscribe Buttons WordPress plugin version 1.4.1 and earlier, presenting a critical stored cross-site scripting vulnerability that can be exploited by users with minimal privileges. This flaw resides within the plugin's handling of user input during post creation or editing processes, where malicious payloads can be injected and subsequently executed when other users view the affected content. The vulnerability specifically targets the plugin's ability to process and display podcast subscription button configurations, which are typically added through post editor interfaces. Attackers with roles that permit post editing or creation can leverage this weakness to inject malicious scripts that will execute in the browsers of other users who access the affected posts.
The technical implementation of this vulnerability stems from insufficient input validation and output sanitization within the plugin's codebase. When users create or modify posts containing podcast subscription buttons, the plugin fails to properly sanitize user-supplied data before storing it in the database. This stored data is then retrieved and rendered in subsequent page views without adequate security measures to prevent script execution. The vulnerability is classified as a stored XSS attack because the malicious payload is permanently stored on the server and executed each time the affected content is accessed, rather than requiring a direct user interaction with a malicious link. This characteristic makes the attack more persistent and dangerous compared to reflected XSS vulnerabilities.
The operational impact of CVE-2021-24743 extends beyond simple data theft or defacement, as it can enable attackers to perform a wide range of malicious activities through compromised user sessions. An attacker could inject scripts that steal authentication cookies, redirect users to malicious websites, or execute commands on behalf of the victim. The vulnerability affects any WordPress installation using the affected plugin version, making it particularly dangerous for sites where multiple users have editing privileges, including contributors, editors, or authors. The attack vector is relatively simple to exploit, requiring only standard post editing capabilities, which means that even users with limited administrative privileges can potentially compromise the entire site's security. This makes the vulnerability particularly concerning for WordPress environments where user role management is not strictly enforced.
Security mitigations for this vulnerability primarily involve immediate plugin updates to version 1.4.2 or later, which contain proper input sanitization and output encoding mechanisms. Organizations should also implement additional defensive measures such as restricting user roles and capabilities to minimize the attack surface, implementing content security policies to prevent script execution, and monitoring for suspicious activity in post creation or modification. The vulnerability aligns with CWE-79, which describes cross-site scripting flaws, and represents a common pattern of insufficient input validation that appears frequently in web applications. From an ATT&CK framework perspective, this vulnerability maps to technique T1566.001, which involves social engineering through spearphishing with a malicious attachment or link, as attackers can craft malicious posts that appear legitimate to unsuspecting users. Regular security audits of WordPress plugins and maintaining updated security practices are essential for preventing similar vulnerabilities from compromising WordPress environments. The incident underscores the importance of proper input validation and output encoding in web applications, particularly in content management systems where user-generated content is prevalent.