Report is an extension that, very simply, allows reporting revisions, hence the name.
The extension is now on Wikimedia Gerrit (GitHub mirror) (Phabricator mirror)
From the root directory of your wiki, run the following commands:
cd extensions
git clone https://github.com/Kenny2github/Report.git
Then add the following line to your LocalSettings.php:
wfLoadExtension( 'Report' );
Finally, from the root directory of your wiki, run the following commands:
cd maintenance
php update.php
This will create the necessary tables that the extension needs.
Once it's installed, it's in use! The extension adds links next to every revision for reporting them, all of which lead to Special:Report.
For admins, simply navigate to Special:HandleReports to view reports that need handling.