CVE-2021-36893 in Responsive Tabs Plugin
Summary
by MITRE • 04/12/2022
Authenticated (author or higher user role) Stored Cross-Site Scripting (XSS) vulnerability in Responsive Tabs (WordPress plugin)
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Analysis
by VulDB Data Team • 04/14/2022
The vulnerability CVE-2021-36893 represents a stored cross-site scripting flaw within the Responsive Tabs WordPress plugin that affects users with author or higher privileges. This issue arises from insufficient input validation and output sanitization mechanisms within the plugin's codebase, specifically when processing user-generated content within tab configurations. The vulnerability is classified as authenticated XSS because it requires a user with at least author-level permissions to exploit the flaw, making it particularly concerning for WordPress environments where multiple users with varying permission levels exist.
The technical implementation of this vulnerability stems from the plugin's failure to properly sanitize user input before storing and subsequently rendering tab content. When an authenticated user creates or modifies tabs containing malicious script payloads, the plugin stores these inputs without adequate filtering or encoding. This allows attackers to inject malicious JavaScript code that executes in the context of other users who view the affected tabs. The stored nature of the vulnerability means that the malicious payload persists in the database and affects all users who access the vulnerable content, unlike reflected XSS attacks that require specific user interaction with malicious links.
From an operational perspective, this vulnerability poses significant risks to WordPress installations using the Responsive Tabs plugin, particularly in environments where multiple content creators or editors exist. The impact extends beyond simple script execution as it can potentially enable attackers to steal session cookies, perform unauthorized actions on behalf of users, or redirect victims to malicious sites. The vulnerability's authenticated nature limits its exploitation surface but does not eliminate the threat, as it can be leveraged by compromised accounts or through social engineering to gain unauthorized access to sensitive user data. This type of vulnerability commonly maps to CWE-79: Improper Neutralization of Input During Web Page Generation, which is a fundamental weakness in web application security.
The attack vector for this vulnerability typically involves an attacker with author privileges accessing the plugin's tab configuration interface and inserting malicious JavaScript code into tab titles or content fields. When other users with sufficient privileges view the affected tabs, the stored script executes in their browsers, potentially leading to session hijacking, data exfiltration, or further compromise of the WordPress installation. Security practitioners should note that this vulnerability aligns with ATT&CK technique T1566.001: Phishing, as attackers may use the XSS to redirect users to malicious sites or harvest credentials. The risk assessment for this vulnerability should consider the plugin's user base, the typical permission levels of WordPress installations, and the potential for privilege escalation through session hijacking or credential theft.
Mitigation strategies for CVE-2021-36893 should include immediate plugin updates to versions that address the stored XSS vulnerability, which typically involves implementing proper input sanitization and output encoding mechanisms. Administrators should also consider implementing additional security measures such as content security policies to limit script execution, regular security audits of user-generated content, and monitoring for suspicious activity in tab configuration areas. The vulnerability highlights the importance of input validation at multiple points in web applications and demonstrates how even authenticated users can introduce security risks through insufficient sanitization of user inputs. Organizations should also implement principle of least privilege concepts to limit the impact of potential compromise, ensuring that users with author roles cannot inadvertently introduce security vulnerabilities that affect the entire WordPress installation.