Currently users can bypass username blacklisting (in MediaWiki:Titleblacklist, [[mw:Extension:Title blacklist]]) by opening an account on another wiki and have an account with the same username via CentralAuth on the wikis where this name is disallowed in titleblacklist.
CentralAuth should check whether the username is allowed on a wiki before creating an account on it for a global user.
Version: unspecified
Severity: normal