MediaWiki's comment based strip markers (e.g. <!--LINK 0:0-->) should include quotes to avoid being included in attributes (advanced task)
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The MediaWiki parser puts markers like <!--LINK 0:0-->
as a placeholder for links which gets replaced with real links later on. (see includes/parser/Parser.php, especially Parser::replaceInternalLinks()
and includes/parser/LinkHolderArray.php)
However, <span title="<!--LINK 0:0-->">
is perfectly valid html which would be broken by the replacement.
As a hardening measure, we should change the marker to be <!--LINK '" 0:0-->
so that it would never be in an attribute of valid html.
See the phabricator ticket for more details.
You are expected to provide a patch in Wikimedia Gerrit. See https://www.mediawiki.org/wiki/Gerrit/Tutorial for how to set up Git and Gerrit.