Thanks for taking the time to report this!
Where is the code of that extension located nowadays? https://www.mediawiki.org/wiki/Extension:QrCode links to SVN which is dead nowadays (and also leads to the question how maintained that code is). That page also says "MediaWiki 1.12 - 1.17.x" but we're at 1.25 nowadays. Has anyone tested whether that extension works in recent MediaWiki versions? What were the results?
Furthermore, this extension has not been deployed on any Wikimedia site yet. Hence it needs to be reviewed first before this request can be fulfilled. Please see Review for deployment for how to proceed.