Mattermost Server is vulnerable to XSS through lack of link relationship attributes `noreferrer` and `noopener`

published 2020-06-19 6 y ago modified 2026-06-17 4 mo ago also GHSA-h3qg-w9j5-wh3m , GO-2025-4058 , EUVD-2016-2060

cvss: 6.1; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.7%; EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits: 0; none known

An issue was discovered in Mattermost Server before 3.1.0. It allows XSS because the noreferrer and noopener protection mechanisms were not in place.

Patch / fix

fixed in 2 distros 1

go github.com/mattermost/mattermost-server 3.1.0, 3.1.0+incompatible
mattermost mattermost_server 3.1.0

govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
govulncheck-vulndb openSUSE Tumbleweed 0.0.20251105T184115-1.1

opensuse advisories openSUSE-SU-2026:21483-1 openSUSE-SU-2025:15710-1

Exploit prediction

0.69% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	6.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:N/I:P/A:N
GitHub	3.1	6.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
go	github.com/mattermost/mattermost-server	<3.1.0 <3.1.0+incompatible	3.1.0 3.1.0+incompatible

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

mattermost.com /security-updates/
vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2016-11071
advisory
github.com /mattermost/mattermost
package
mattermost.com /security-updates
web
github.com /advisories/GHSA-h3qg-w9j5-wh3m
advisory

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary