Riskcovery

CVE-2026-42857

Open edX Platform: Stored CSS Injection in Email Notifications via Incomplete HTML Sanitization

State
Published
Severity
4.6 Medium
Published
May 11, 2026
Updated
May 13, 2026
Reserved
Apr 30, 2026

Read the record on cve.org

Description

Open edX Platform enables the authoring and delivery of online learning at any scale. The HTML sanitizer clean_thread_html_body() used for discussion notification emails fails to remove <style> tags from user-generated discussion post content. This content is rendered with Django's |safe template filter in email notification templates, allowing any enrolled student to inject arbitrary CSS into email notifications sent to other users. This enables email tracking (IP address disclosure), content spoofing, and phishing attacks. This vulnerability is fixed with commit cddc25cd791bb78f76833896e4778f668861df12.

Scores

CVSSScoreVectorSource
3.14.6 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:NGitHub_M

Weaknesses

  • CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Affected Products

ProductVersions
openedx-platformopenedx
  • < cddc25cd791bb78f76833896e4778f668861df12Affected
  • >= sumac, < ulmoAffected

References

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