Manual:$wgExtensionCredits

Details
An array of extension types and inside that their names, versions, authors and urls. This credit information get added to the wiki's Special:Version page, allowing users to see which extensions are installed, and find more information about them.

This is not a configuration settings mentioned in LocalSettings.php. Typically extension developers will write code which appends to the array contained in this global variable.

See Manual:Extensions

Usage
Extension developers can append to the array with the following code:

Version and url keys are optional, and can be omitted.

$type must be one of the following:
 * specialpage
 * parserhook
 * variable (added in 1.6.0)
 * other

Description and author fields get parsed as wiki syntax.