Stored XSS vulnerability on Bounce Management Callback
Impact
Insufficient sanitization / filtering allows for arbitrary JavaScript Injection in Mautic using the bounce management callback function. The values submitted in the "error" and "error_related_to" parameters of the POST request of the bounce management callback will be permanently stored and executed once the details page of an affected lead is opened by a Mautic user.
An attacker with access to the bounce management callback function (identified with the Mailjet webhook, but it is assumed this will work uniformly across all kinds of webhooks) can inject arbitrary JavaScript Code into the "error" and "error_related_to" parameters of the POST request (POST /mailer/<product / webhook>/callback). It is noted that there is no authentication needed to access this function.
The JavaScript Code is stored permanently in the web application and executed every time an authenticated user views the details page of a single contact / lead in Mautic. This means, arbitrary code can be executed to, e.g., steal or tamper with information.
Patches
Upgrade to 3.3.4 or 4.0.0
Workarounds
No
References
https://github.com/mautic/mautic/releases/tag/3.3.4 https://github.com/mautic/mautic/releases/tag/4.0.0
For more information
If you have any questions or comments about this advisory:
- Email us at security@mautic.org
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | mautic/core | < 3.3.4, >= 4.0.0-alpha1, < 4.0.0 | 3.3.4, 4.0.0 |
References
- https://github.com/mautic/mautic/security/advisories/GHSA-86pv-95mj-7w5f
- https://nvd.nist.gov/vuln/detail/CVE-2021-27910
- https://github.com/mautic/mautic/commit/e6a405975342f3cf86aa71927618d31d25135fa3
- https://github.com/FriendsOfPHP/security-advisories/blob/master/mautic/core/CVE-2021-27910.yaml
- https://github.com/mautic/mautic
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N- Weakness (CWE)
CWE-79- Platform
- Composer
- Package
mautic/core- Disclosed
- 01.09.2021
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-86pv-95mj-7w5f - 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
-
Stored XSS vulnerability on Bounce Management Callback this entry
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