High 8.0Published Mar 5, 2026

CVE-2026-28405MarkUs: Stored XSS in Submission HTML Preview Enables Instructor-Context Actions

Updated under an hour ago (Oct 26, 2026, 7:40 AM ET)

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It affects MarkUsProject Markus. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for MarkUsProject Markus

Exploited in the last 30 days

MarkUs is a web application for the submission and grading of student assignments. Prior to version 2.9.1, the courses/<:course_id>/assignments/<:assignment_id>/submissions/html_content route reads the contents of a student-submitted file and renders them without sanitization. This issue has been patched in version 2.9.1.

CVSS: 8.0 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Weakness (CWE): CWE-79
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Mar 6, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

MarkUsProject Markus markusproject:markus (from the name)	before 2.9.1	CNA record
markusproject markus markusproject:markus	before 2.9.1	NVD

References

https://github.com/MarkUsProject/Markus/security/advisories/GHSA-p5pc-pxrj-3893x-refsource-confirm, vendor-advisory
https://github.com/MarkUsProject/Markus/commit/55d74f2ddb72d2ec2f29aa2b4cb6b2da10755036x-refsource-misc, patch
https://github.com/MarkUsProject/Markus/releases/tag/v2.9.1x-refsource-misc, release-notes

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.