Without letting you know, it deletes CATEGORIES and TAGS from your posts.
It happened to me twice, first time I was thinking - my mistake, I did not see the option for Categories, and it was easy to fix, just a several articles.
This time, on the website of 27,000 magazine news posts, it killed the whole structure. It is costing us 2 days of programmer's time to fix it (so far).
BEWARE!
BTW, All - I mean all - DB Messing Plugins should come with the DB auto backup/restore feature...