In https://phabricator.wikimedia.org/rMW73224f4f8b8a26b9a9a04e338bb1c3c2f163a820 several methods of the User class were deprecated. Methods of the UserGroupMembership class should be used instead, and the function calls are not exactly identical.
Running a grep for makeGroupLinkHTML on all extensions indicated that these use cases currently exist and need to be updated:
extensions/WikiForum/includes/WikiForum.class.php: User::makeGroupLinkHTML( 'sysop', User::getGroupMember( 'sysop', $username ) ) extensions/WikiForum/includes/WikiForum.class.php: User::makeGroupLinkHTML( 'forumadmin', User::getGroupMember( 'forumadmin', $username ) ) extensions/CheckUser/specials/SpecialCheckUser.php: $cache[$group] = User::makeGroupLinkHTML( extensions/ConfirmAccount/frontend/specialpages/actions/UserCredentials_body.php: $list[] = User::makeGroupLinkHTML(
A similar check should be conducted for other deprecated functions as well.
This is a parent task; for each extension a subtask can be created, or a patch can be submitted towards this parent task.