CVE-2026-28405

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

8.0 High

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: Required

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

0.26%Up 0.2 points since Mar 6, 2026

What each source reports

CVE List Score used 8.0

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

Record: CVE-2026-28405
CVSS 3.1: 8.0 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Weakness: CWE-79
Updated: 2026-11-02

EUVDEUVD-2026-9870 8.0

Record: EUVD-2026-9870
CVSS 3.1: 8.0 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Updated: 2026-11-02

NVD 8.0

Record: CVE-2026-28405
CVSS 3.1: 8.0 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSV 8.0

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

Record: CVE-2026-28405
CVSS 3.1: 8.0 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
Weakness: CWE-79
Updated: 2026-11-02

Affected products

markusproject markus

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-28405 is a high vulnerability (CVSS 8.0) in Markusproject Markus, published March 5, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.26%, the 17th percentile. No source names a fixed version.