Description
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the iframe src traversal guard did not treat literal backslashes as path separators after decoded dot segments. A crafted source could therefore pass an allowed_iframes subpath check while browser URL normalization moved the iframe outside the intended allowed path. The resulting iframe could load content from a location that the administrator did not allow. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
References6
- github.com/discourse/discourse/commit/042d7b159beda4f74d23e245e…
- github.com/discourse/discourse/commit/097ce5600a2d74d9c68e57974…
- github.com/discourse/discourse/commit/0b5a27e689925edce9ba9b141…
- github.com/discourse/discourse/commit/142f5155ad8e56ddb8012c4e7…
- github.com/discourse/discourse/pull/42882
- github.com/discourse/discourse/security/advisories/GHSA-6pwj-wg…
Metrics
- CVSS 3.1
-
7.2
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - EPSS — exploit probability
- 0% percentile: 21 · as of 9 November 2026
- CWE
- CWE-22
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.