I have noticed a bug on two forums where if a topic is moved from a private category, which users do not have access to, to a public category which users do - the private category shows in the edits menu. See the example below.
I do not have access to the “Admin Only” category yet it shows anyway. Clicking on the category brings a 404 error.
To repro:
1.) Create a topic in the Staff category in the forum.
2.) After 5-10 minutes, move that topic to a public area of the forum.
3.) Log onto an account that does not have access to the Staff category and check the edit history.
Maybe it could hide the original category from users, who cannot see that category. Then the history would look like that of a post which was moved from a PM to its own public topic.