Open edX Platform: Stored CSS Injection in Email Digest Notifications via Unsanitized Thread Title (incomplete patch of CVE-2026-42857)
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Open edX Platform enables the authoring and delivery of online learning at any scale. From Redwood until Ulmo and Verawood.1, the add_additional_attributes_to_notifications function in openedx/core/djangoapps/notifications/email/utils.py assigns notification content without sanitizing discussion-title values produced by get_notification_content in openedx/core/djangoapps/notifications/base_notification.py. An enrolled student can place CSS-capable markup in the post_title value supplied by lms/djangoapps/discussion/rest_api/discussions_notifications.py. Digest and batched-email rendering then passes that value through openedx/core/djangoapps/notifications/templates/notifications/digest_content.html as safe HTML, allowing email-open tracking and content spoofing or phishing when another learner opens a CSS-rendering client. The immediate-email path is not affected because it strips title markup and renders a separately sanitized body. This issue is fixed in Ulmo and Verawood.1.
Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.
No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.
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