Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the topic small-action and nested-activity-log components interpolated the free-form action_code_who value into mention-link href attributes without URL encoding. A quote-bearing display name could terminate the intended URL attribute and inject attacker-controlled elements into the trusted rendered markup.
Although the visible mention text was escaped, the unencoded path component allowed stored HTML injection when another user viewed the affected topic action or activity log. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
Low
Partial data leak
Integrity
Low
Partial data modification
Availability
None
No disruption
CVSS Vector v3.1
Weakness Type (CWE)
References 6
https://github.com/discourse/discourse/commit/20dbf112760eb1d6a58f2e49aeef75468…
security-advisories@github.com
https://github.com/discourse/discourse/commit/66653c484cfb91bc346f9a326f6945387…
security-advisories@github.com
https://github.com/discourse/discourse/commit/77a81c7a3a7ff9e94b355e32b8f379f2d…
security-advisories@github.com
https://github.com/discourse/discourse/commit/c4748f651d9d2f3a6dd3106a4d5564536…
security-advisories@github.com
https://github.com/discourse/discourse/pull/42882
security-advisories@github.com
https://github.com/discourse/discourse/security/advisories/GHSA-pv3p-p3m9-v8v3
security-advisories@github.com