Unlike other global objects, it doesn't have a wg prefix ([[mw:wg]]), its name is so common, and it's even not mentioned in [[mw:Manual:Global object variables]].

Found in IRC log (MediaWiki-General):

SleePy: Some reason after calling require( $maintenance->loadSettings() ); in doMaintenance.php it seems to set the $maintenance object to 0;

SleePy: Oh I think I found it, has to do with a integration file for authentication which is calling its own $maintenance

Version: 1.22.0
Severity: normal