CVE-2025-9823: mautic Cross-site Scripting

Vulnerability summary

CVE-2025-9823 is a medium (CVSS 4.8) Cross-site Scripting vulnerability in mautic. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 23.3% of scored vulnerabilities.

Timeline

1. 03-09-2025
   PublishedVulnerability first disclosed.
2. 03-09-2025
   Last modifiedVulnerability information updated.

Description

SummaryA Cross-Site Scripting (XSS) vulnerability allows an attacker to execute arbitrary JavaScript in the context of another user’s session. This occurs because user-supplied input is reflected back in the server’s response without proper sanitization or escaping, potentially enabling malicious actions such as session hijacking, credential theft, or unauthorized actions in the application. DetailsThe vulnerability resides in the “Tags” input field on the /s/ajax?action=lead:addLeadTags endpoint. Although the server applies sanitization before storing the data or returning it later, the payload is executed immediately in the victim’s browser upon reflection, allowing an attacker to run arbitrary JavaScript in the user’s session. ImpactA Reflected XSS attack can have a significant impact, allowing attackers to steal sensitive user data like cookies, redirect users to malicious websites, manipulate the web page content, and essentially take control of a user's session within an application by executing malicious JavaScript code within the victim's browser, even if the server-side code is secure; essentially enabling them to perform actions as if they were the logged-in user. References * Web Security Academy: Cross-site scripting https://portswigger.net/web-security/cross-site-scripting * Web Security Academy: Reflected cross-site scripting https://portswigger.net/web-security/cross-site-scripting/reflected

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.