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CRITICAL severity

CVE-2020-35129 — core

CRITICAL

CVE-2020-35129 is a critical-severity (CVSS 9) Cross-site Scripting (XSS) vulnerability in mautic/core. A fix is available for mautic/core — see the affected versions and patch details below.

Mautic stored Cross-site Scripting (XSS)

Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.0%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs63th percentile — riskier than 63% of all scored CVEsHighest risk
0.12%0.58%1.05%1.52%0.6%1.0%May 26Aug 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected
🐘mautic/core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Mautic before 3.2.4 is affected by stored XSS. An attacker with access to Social Monitoring, an application feature, could attack other users, including administrators. For example, an attacker could load an externally drafted JavaScript file that would allow them to eventually perform actions on the target user’s behalf, including changing the user’s password or email address or changing the attacker’s user role from a low-privileged user to an administrator account.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistmautic/coreall versions3.2.4composer require mautic/core:^3.2.4

Affected Products

1 product · 1 configurations
Application
mauticmautic
< 3.2.4
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mautic/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update mautic/core to 3.2.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-35129 is resolved across your whole dependency graph.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

Mautic before 3.2.4 is affected by stored XSS. An attacker with access to Social Monitoring, an application feature, could attack other users, including administrators. For example, an attacker could load an externally drafted JavaScript file that would allow them to eventually perform actions on the target user’s behalf, including changing the user’s password or email address or changing the attacker’s user role from a low-privileged user to an administrator account.
O3 Security · Impact-Aware SCA

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CVE-2020-35129: core XSS — Fixed in 3.2.4