I am not a hacker but it was easy for me as registered user of the the wiki to find out which version is installed:
According to https://wiki.manjaro.org/index.php?title=Special:Version it is Version 1.22.5.
On the site of Mediawiki at https://www.mediawiki.org/wiki/News they state the date of publishing this version was 2014-03-27.
At https://www.mediawiki.org/wiki/Download they state:
To users of MediaWiki versions 1.30 and earlier: Support of these branches was discontinued. Please update to a newer version of MediaWiki: