I have randomly viewed my own CentralAuth information ( https://meta.wikimedia.org/wiki/Special:CentralAuth/Base ) and discovered that I have local steward flags on the following closed wikis:
- wikimania2014wiki
- amwikiquote
- angwikibooks
I could not find any local or Meta logs granting me the permissions. Nor do other stewards have the flags there.
I am indeed a steward so assuming there were no other random permission assignments it is not a security issue per se, but it's better to check that there weren't such.