CVE-2023-25172: Discourse vulnerable to Cross-site Scripting - user name displayed on post

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-03-17 · updated 2026-06-17
Weakness: CWE-79

Description

Discourse is an open-source discussion platform. Prior to version 3.0.1 of the `stable` branch and version 3.1.0.beta2 of the `beta` and `tests-passed` branches, a maliciously crafted URL can be included in a user's full name field to to carry out cross-site scripting attacks on sites with a disabled or overly permissive CSP (Content Security Policy). Discourse's default CSP prevents this vulnerability. The vulnerability is patched in version 3.0.1 of the `stable` branch and version 3.1.0.beta2 of the `beta` and `tests-passed` branches. As a workaround, enable and/or restore your site's CSP to the default one provided with Discourse.

Affected products

discourse: before 3.0.1; before 3.1.0; 3.1.0-beta1 — fixed in 3.0.1, 3.1.0

How to fix

Upgrade to a fixed version: discourse 3.0.1, 3.1.0. Check the vendor advisory for mitigations.

References

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