Manual:$wgExtensionCredits

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

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

See Manual:Extensions

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

The version and url keys are optional, and can be omitted.

In version 1.12 and newer, descriptionmsg will override description. The value of descriptionmsg will be treated as the name of the message used for the description.

$type must be one of the following:
 * specialpage - extensions that add special pages
 * parserhook - extensions that modify, add or replace functionality in the MediaWiki parser
 * variable (added in 1.6.0)
 * media (added in 1.11) - media handlers
 * other

Description and author fields get parsed as wiki syntax.