CVE-2026-73378 in Contact Form Plugin
Summary
by MITRE • 08/18/2026
Unauthenticated Cross Site Scripting (XSS) in Contact Form by Supsystic < 1.10.0 versions.
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Analysis
by VulDB Data Team • 08/18/2026
The vulnerability identified as an unauthenticated cross-site scripting flaw within the contact form functionality of Supsystic plugins prior to version 1.10.0 represents a significant security risk for websites utilizing these components. This specific weakness stems from insufficient input validation and sanitization mechanisms when processing user-submitted data through the public-facing contact forms. Because the vulnerability is unauthenticated, it does not require any form of user login or privilege escalation, allowing any internet user with access to the vulnerable page to exploit the flaw directly. The core technical issue lies in the application's failure to properly encode special characters within user inputs before rendering them back into the browser context. When a victim visits a webpage containing maliciously crafted script tags embedded within the contact form fields, the browser executes these scripts as if they were legitimate content from the site itself. This behavior aligns with CWE-79, which classifies improper neutralization of input during web page generation, commonly known as cross-site scripting. The attack vector is typically classified under ATT&CK technique T1059, specifically involving command and script interpretation through browser-based execution, allowing attackers to bypass standard security controls that rely on authentication requirements for sensitive operations.
The operational impact of this vulnerability extends beyond simple defacement or nuisance alerts. Attackers can leverage the executed JavaScript to perform session hijacking by stealing cookies containing session tokens, thereby gaining unauthorized access to user accounts if those users are logged in at the time of exploitation. Furthermore, malicious scripts can redirect victims to phishing sites designed to harvest credentials or install malware on the victim's system through drive-by downloads. In more sophisticated scenarios, attackers might use the vulnerability to perform cross-site request forgery attacks by manipulating the authenticated state of other users who visit the compromised page. The persistence of this risk is heightened because contact forms are often among the most frequently accessed and interacted-with elements on a website, increasing the likelihood of successful exploitation through social engineering tactics such as embedding malicious links in emails or forums that direct victims to the vulnerable form.
Mitigation strategies must prioritize immediate remediation by updating the Supsystic plugin to version 1.10.0 or later, where these input validation issues have been addressed. For organizations unable to update immediately due to compatibility constraints, implementing a Web Application Firewall is recommended as an interim control layer. The firewall should be configured with rules that detect and block common XSS payloads, such as script tags, event handlers like onerror or onload, and encoded variations of malicious JavaScript code within form submission parameters. Additionally, developers should enforce strict Content Security Policy headers to restrict the sources from which scripts can be loaded, thereby limiting the impact even if an injection attempt succeeds. Regular security audits focusing on input handling in public-facing forms are essential to prevent similar vulnerabilities from being introduced during future development cycles or plugin updates.