Manual:Extension support/1.12/ExtDowngrading

SpecialPage localization
The SpecialPage localization of extensions using $wgExtensionAliasesFiles is no longer available. You can always instruct users to localize by hand or include your localization file by editing the core and following the 1.13 Upgrading procedure in your extension. Please note that $specialPageAliaseswas introduced in 1.9, but $aliases can be used before that with the code outlined.