GHSA-7j9p-67mm-5g87

Problem

TL;DR: Any LTI tool that is integrated with on the Open edX platform can post a grade back for any LTI XBlock so long as it knows or can guess the block location for that XBlock.

In LTI 1.3, LTI tools can "pass back" scores that learners earn while using LTI tools to the edX platform. The edX platform then stores those LTI scores in a separate table. If the right conditions are met, these scores are then persisted to the LMS grades tables.

LTI tools can create what are called "line items" on the edX platform. A line item can be thought of as a column in a grade book; it stores results for a specific activity (i.e. XBlock) for a specific set of users (i.e. users in the course using the XBlock). A line item has an optional resourcelinkid field, which is basically the XBlock location. An LTI tool can supply any value for this field.

An LTI tool submits scores to the edX platform for line items. The code that uploads that score to the LMS grade tables determines which XBlock to upload the grades for by reading the resourcelinkid field of the associated line item. Because the LTI tool could have submitted any value for the resourcelinkid field, this introduces the potential for a nefarious LTI tool to submit scores for any LTI XBlock on the platform.

Impact

Any LTI tool that is integrated with on the Open edX platform can post a grade back for any LTI XBlock so long as it knows the resourcelinkid (i.e. block location) for that XBlock.

The impact is a loss of integrity for LTI XBlock grades.

Patches

No available patch

Workarounds

No