HTML injection with AutoComplete suggestions

How it was found

1. As user1 set your displayname to <a href="https://nextcloud.com">Name</a>
2. As user2 autocomplete the name in the comments input (or Talk chat input)
3. Click on the user name you just autocompleted

User2 is redirected to https://nextcloud.com

Only works with HTML, not with script

Impact

User1 can trick user2 to render any html