CVE-2021-24202 in Elementor Website Builder Plugin
Summary
by MITRE • 04/06/2021
In the Elementor Website Builder WordPress plugin before 3.1.4, the heading widget (includes/widgets/heading.php) accepts a ‘header_size’ parameter. Although the element control lists a fixed set of possible html tags, it is possible for a user with Contributor or above permissions to send a modified ‘save_builder’ request with this parameter set to ‘script’ and combined with a ‘title’ parameter containing JavaScript, which will then be executed when the saved page is viewed or previewed.
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Analysis
by VulDB Data Team • 04/10/2021
The vulnerability identified as CVE-2021-24202 affects the Elementor Website Builder WordPress plugin, specifically targeting versions prior to 3.1.4. This security flaw resides within the heading widget implementation at includes/widgets/heading.php where the plugin fails to properly validate user input for the header_size parameter. The vulnerability represents a classic cross-site scripting issue that exploits improper input sanitization and validation mechanisms. Attackers with Contributor level permissions or higher can manipulate the save_builder request to inject malicious javascript code through the title parameter, creating a persistent threat vector that executes when the compromised page is viewed or previewed.
The technical implementation of this vulnerability stems from inadequate parameter validation within the Elementor plugin's widget handling system. While the plugin's element control does define a fixed set of acceptable HTML tags for the header_size parameter, the validation logic fails to properly enforce these constraints. When a malicious user submits a request with header_size set to 'script' in combination with javascript code within the title parameter, the system processes this input without proper sanitization. This creates a scenario where user-controllable data bypasses the intended security boundaries, allowing arbitrary code execution in the context of the victim's browser. The vulnerability aligns with CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') and represents a privilege escalation vector through which lower-privileged users can achieve elevated attack capabilities.
The operational impact of this vulnerability extends beyond simple XSS exploitation, as it provides attackers with the ability to execute persistent malicious code within the context of legitimate website visitors. When compromised pages are viewed or previewed, the injected javascript executes automatically, potentially leading to session hijacking, data exfiltration, or redirection to malicious sites. The vulnerability affects not just individual user sessions but can compromise the entire website's integrity and user trust. Since the attacker only requires Contributor permissions or higher, which are commonly granted to content editors and administrators, this creates a significant risk for websites with multiple user roles. The attack can be particularly damaging in environments where the plugin is used for corporate websites, customer portals, or any site where user-generated content is processed and displayed.
Mitigation strategies for CVE-2021-24202 should prioritize immediate plugin updates to version 3.1.4 or later, where the vulnerability has been addressed through proper input validation and sanitization. Organizations should implement comprehensive security monitoring to detect unauthorized modifications to website content and establish strict access controls limiting user permissions to only what is necessary for their roles. The fix typically involves implementing proper input validation that explicitly rejects non-allowed HTML tag values and ensuring that all user-provided content undergoes strict sanitization before being stored or rendered. Additionally, organizations should consider implementing web application firewalls and content security policies to add defensive layers against similar injection attacks. This vulnerability demonstrates the importance of proper input validation and the principle of least privilege in web application security, aligning with ATT&CK techniques related to privilege escalation and code injection.