Ultimate Member < 2.1.20 - Authenticated Reflected Cross-Site Scripting (XSS)
The plugin did not properly sanitise, validate or encode the query string when generating a link to edit user's own profile, leading to an authenticated reflected Cross-Site Scripting issue. Knowledge of the targeted username is required to exploit this, and attackers would then need to make the related logged in user open a malicious link.
Proof of Concept
Log on to the blog and open the following link: https://example.com/user/[your username]/?"><script>alert("XSS")</script>