Craft CMS stored XSS in indexedVolumes

Summary

XSS can be triggered via the Update Asset Index utility

PoC

1. Access setting tab
2. Create new assets
3. In assets name inject payload: "<script>alert(26)</script>
4. Click Utilities tab
5. Choose all volumes, or volume trigger xss
6. Click Update asset indexes.

XSS will be triggered

Json response volumes name makes triggers the payload

"session":{"id":1,"indexedVolumes":{"1":"\"<script>alert(26)</script>"},

It’s run on every POST request in the utility.

Resolved in https://github.com/craftcms/cms/commit/8c2ad0bd313015b8ee42326af2848ee748f1d766