CVE-2025-9823 Reflected XSS in lead:addLeadTags - Quick Add
Reflected XSS in Mautic allows attackers to execute arbitrary JavaScript in victim sessions, enabling session hijacking and data theft.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2025-9823?
CVE-2025-9823 is a medium-severity cross-site scripting vulnerability in Mautic, published on 3 Sep 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official 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
Weakness: CWE-79
Which versions are affected by CVE-2025-9823?
6 open source packages ship an affected version, including mautic/core.
| Package | Affected | Fixed in |
|---|---|---|
mautic/core Packagist | From 4.4.0 | 4.4.17 |
mautic/core Packagist | From 4.4.0 | 4.4.17 |
mautic/core Packagist | From 5.0.0-alpha | 5.2.8 |
mautic/core Packagist | From 5.0.0-alpha | 5.2.8 |
mautic/core Packagist | From 6.0.0-alpha | 6.0.5 |
mautic/core Packagist | From 6.0.0-alpha | 6.0.5 |
How do I fix CVE-2025-9823?
Upgrade mautic/core to a fixed version for your release line: 4.4.17, 5.2.8 or 6.0.5.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2025-9823 being exploited?
There is no known exploitation of CVE-2025-9823 in the wild and no public exploit code.
Sources
Also known as GHSA-9v8p-m85m-f7mm.