Steps to reproduce:
1. Tag a page with "hello" and "world"
2. Go to <server>/xwiki/bin/view/Main/Tags?do=deleteTag&tag=hello
3. Go to <server>/xwiki/bin/view/Main/Tags?do=renameTag&tag=world&renameTo=bye
No tags are deleted or renamed, CSRF errors are displayed in both cases.
Both actions are executed, the tag "hello" has been deleted and "world" has been renamed to "bye".
This demonstrates a CSRF attack, the two URLs could also be called by embedding images with the respective URLs into the content of a page (or another website) and then getting an admin user to visit this page. While both the form for deleting and renaming tags contain the CSRF token, there is no code for verifying the token.