CVE-2016-11070 Mattermost Server is vulnerable to XSS through customizable theme color-code values

What is CVE-2016-11070?

CVE-2016-11070 is a medium-severity cross-site scripting vulnerability in Mattermost Mattermost Server, published on 19 Jun 2020. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

An issue was discovered in Mattermost Server before 3.1.0. It allows XSS via theme color-code values.

Weakness: CWE-79

Which versions are affected by CVE-2016-11070?

3 open source packages ship an affected version, including github.com/mattermost/mattermost-server. It affects 1 product.

Products include Mattermost Mattermost Server.

How do I fix CVE-2016-11070?

Upgrade github.com/mattermost/mattermost-server to a fixed version for your release line: 3.1.0 or 3.1.0+incompatible.

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-2016-11070 being exploited?

There is no known exploitation of CVE-2016-11070 in the wild and no public exploit code.

Other vulnerabilities in Mattermost Mattermost Server

• CVE-2025-12419 Account takeover on OAuth/OpenID-enabled servers Critical 9.9
• CVE-2025-12421 Account Takeover via Code Exchange Endpoint Critical 9.9
• CVE-2025-4981 Path Traversal Leading to RCE by Any Authenticated Mattermost User Critical 9.9
• CVE-2025-20051 Arbitrary file read via block duplication in Mattermost Boards Critical 9.9
• CVE-2025-25279 Arbitrary file read in Mattermost Boards via import & export board archive Critical 9.9

All Mattermost Mattermost Server vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-h8qw-xqm9-q66j, GO-2025-4050.