CVE-2026-42857: Open edX Platform: Stored CSS Injection in Email Notifications via Incomplete HTML Sanitization
openedx · openedx-platform
Affected: openedx-platform · Exploitation: unlikely (under 1%)
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 8% of scored CVEs
DescriptionCVE.org
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.
Affected products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- openedx · openedx-platform< cddc25cd791bb78f76833896e4778f668861df12; >= sumac, < ulmo
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Unlikely (under 1%). EPSS under 1%, or no score yet.
- CISA KEV
- Not listed
- Public check
- No public nuclei template
- Weakness
- Cross-site Scripting
- Vendor
- openedx
- Published
- May 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-42857 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.