Discourse: Chat upload filenames rendered as raw HTML in excerpts
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, attacker-controlled upload filenames used in chat message excerpts were rendered as unescaped HTML. A user able to upload a file and send chat content could place markup in a filename that was then interpreted by chat channel lists, chat summary emails, pinned message bars, reply previews, thread previews, and other excerpt renderers. The issue allowed trusted-HTML injection that altered rendered excerpt content, but JavaScript execution was not demonstrated with default Content Security Policy settings. The advisory states that no confidentiality, integrity, or availability impact was identified, while its structured scoring metadata separately assigns low integrity impact. Sites that disable or relax the default CSP have increased exposure. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
CVE-2026-91121
Primary source · Revision 2
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-91121
discourse
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"vendor": "discourse",
"product": "discourse",
"versions": [
{
"status": "affected",
"version": "< 2026.8.0"
},
{
"status": "affected",
"version": ">= 2026.7.0-latest, < 2026.7.2"
},
{
"status": "affected",
"version": ">= 2026.6.0-latest, < 2026.6.3"
},
{
"status": "affected",
"version": ">= 2026.1.0-latest, < 2026.1.8"
}
]
}
]- Related CVEs
- CVE-2026-91121
Source reference:
/cveMetadata/cveId
Publisher severity
medium
Source reference: /containers/cna/metrics
- Event
- #59652 · Revision 2
- Added to Heist Feed
- Publisher date