CVE-2026-28405CWE-79

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

High · published March 5, 2026

CVSS v3.1
8.0
EPSS
0%
Percentile
36.9
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
8.0 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.00437 · 36.9th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-03-05T20:06Z
EPSS history
Timeline
  • 05 MAR 20:06Z
    MarkUs: Stored XSS in Submission HTML Preview Enables Instructor-Context Actions
    cvelistv5