Mautic vulnerable to reflected XSS in lead:addLeadTags - Quick Add
Summary
A 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.
Details
The 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.
Impact
A 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
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | mautic/core | >= 4.4.0, < 4.4.17, >= 5.0.0-alpha, < 5.2.8, >= 6.0.0-alpha, < 6.0.5 | 4.4.17, 5.2.8, 6.0.5 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-79- Platform
- Composer
- Package
mautic/core- Disclosed
- 03.09.2025
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-9v8p-m85m-f7mm - CC BY 4.0
Vulnerability history: mautic/core
All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 57
- First → latest
- 01.2021 07.2026
- Without a fix
- 1
- Exploited in attacks
- 0
Severity breakdown
- Critical 9
- High 17
- Medium 29
- Low 2
Disclosures per year
- 2021: 16
- 2022: 7
- 2023: 0
- 2024: 13
- 2025: 13
- 2026: 8
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Mautic vulnerable to reflected XSS in lead:addLeadTags - Quick Add this entry
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