CVE-2021-3135 in tagDiv newspaper Theme
Summary
by MITRE • 07/20/2021
An issue was discovered in the tagDiv Newspaper theme 10.3.9.1 for WordPress. It allows XSS via the wp-admin/admin-ajax.php td_block_id parameter in a td_ajax_block API call.
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Analysis
by VulDB Data Team • 07/22/2021
The vulnerability identified as CVE-2021-3135 affects the tagDiv Newspaper theme version 10.3.9.1 for WordPress platforms, representing a cross-site scripting weakness that could potentially compromise user sessions and execute malicious code within the browser context of affected users. This issue specifically manifests through the wp-admin/admin-ajax.php endpoint which serves as a central API handler for WordPress administrative functions, making it a critical attack vector for malicious actors seeking to exploit the theme's implementation. The vulnerability occurs when the td_block_id parameter within the td_ajax_block API call is not properly sanitized or validated, creating an opening for attackers to inject malicious scripts that will execute in the context of other users who view affected content.
The technical flaw stems from insufficient input validation and output escaping mechanisms within the theme's AJAX handling functionality. When the td_block_id parameter is passed through the td_ajax_block API endpoint, the theme fails to adequately sanitize this input before processing it, allowing attackers to inject script code that gets executed when the page renders. This represents a classic cross-site scripting vulnerability where the malicious payload is stored or transmitted through the application's legitimate API endpoints. The vulnerability is categorized under CWE-79 as a failure to sanitize or escape output, which specifically addresses the issue of unvalidated input being passed to web applications without proper security controls. The attack surface is particularly concerning because it leverages WordPress's built-in AJAX infrastructure which is commonly used for dynamic content loading and administrative functions.
The operational impact of this vulnerability extends beyond simple script execution, as it could enable attackers to perform session hijacking, steal sensitive user information, redirect users to malicious sites, or even escalate privileges within the WordPress environment. Since the vulnerability affects a widely used theme, the potential attack surface is substantial, with numerous WordPress installations potentially compromised. The exploitation requires minimal privileges since the attack targets a legitimate API endpoint that is accessible to authenticated users, making it particularly dangerous for administrators and content creators who regularly access the WordPress admin interface. The vulnerability could also facilitate more sophisticated attacks such as credential theft through session cookie manipulation or the delivery of additional malware payloads through browser-based attacks.
Mitigation strategies for CVE-2021-3135 should prioritize immediate theme updates to version 10.3.9.2 or later, which contain the necessary patches to address the input validation flaws. Organizations should implement comprehensive input sanitization measures within their WordPress environments, including the deployment of web application firewalls that can detect and block malicious payloads targeting known XSS patterns. Security teams should conduct thorough vulnerability assessments to identify other potentially affected themes or plugins within their WordPress installations, as similar vulnerabilities may exist in other third-party components. Additionally, implementing proper output encoding and content security policies can provide additional defense-in-depth measures against similar cross-site scripting attacks. The vulnerability aligns with ATT&CK technique T1213 which covers data from information repositories, and T1566 which covers credential harvesting through social engineering, as attackers could leverage this vulnerability to establish persistent access and harvest user credentials through browser-based attacks. Regular security monitoring and patch management procedures should be enhanced to prevent similar vulnerabilities from being introduced through third-party theme and plugin components, particularly focusing on input validation controls and proper output escaping mechanisms within WordPress administrative APIs.