CVE-2021-39161 Cross-site scripting via category name in Discourse
Attackers can execute scripts via category names in Discourse if Content Security Policy is disabled or modified, potentially leading to account takeover.
- 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-2021-39161?
CVE-2021-39161 is a medium-severity cross-site scripting vulnerability in Discourse Discourse, published on 26 Aug 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Discourse is an open source platform for community discussion. In affected versions category names can be used for Cross-site scripting(XSS) attacks. This is mitigated by Discourse's default Content Security Policy and this vulnerability only affects sites which have modified or disabled or changed Discourse's default Content Security Policy have allowed for moderators to modify categories. This issue is patched in the latest stable, beta and tests-passed versions of Discourse. Users are advised to ensure that the Content Security Policy is enabled, and has not been modified in a way which would make it more vulnerable to XSS attacks.
Weakness: CWE-79
Which versions are affected by CVE-2021-39161?
1 open source package ship an affected version, including discourse. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
discourse Bitnami | All versions | 2.7.8 |
Products include Discourse Discourse.
How do I fix CVE-2021-39161?
Upgrade discourse to 2.7.8 or later.
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-2021-39161 being exploited?
There is no known exploitation of CVE-2021-39161 in the wild and no public exploit code.
Other vulnerabilities in Discourse Discourse
- CVE-2021-41163 RCE via malicious SNS subscription payload
- CVE-2022-36066 Discourse vulnerable to RCE via admins uploading maliciously zipped file
- CVE-2022-39356 Discourse user account takeover via email and invite link
- CVE-2023-22468 Discourse vulnerable to Cross-site Scripting in local oneboxes
- CVE-2026-27934 Discourse leaks private topic title and post excerpt via user action API endpoint
Sources
Also known as BIT-discourse-2021-39161, GHSA-xhmc-9jwm-wqph.