id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc	focuses
66106	get_locale(), get_user_locale() and determine_locale() can return a non-string	jonsurrell		"`get_locale()`, `get_user_locale()` and `determine_locale()` can return a non-string values. All three functions are documented `@return string`, but they read from untyped data sources that may be invalid.

Once an unexpected value gets through, the first just-in-time translation of an unloaded text domain reaches `WP_Textdomain_Registry::set()`, which uses the locale as an array key: `TypeError: Cannot access offset of type array on array`.

This is not theoretical, it was discovered from fatal errors observed in production environments."	defect (bug)	assigned	normal	7.2	I18N		normal		has-patch has-unit-tests