Hi,
If those changes are not intended then you should revert them. You can use the “Revert” link from the line with “Version coming from extension …”. Have you recently upgraded XWiki? You only mentioned upgrading the Firefox version. If you upgraded XWiki maybe you haven’t updated the wiki pages, i.e. maybe you didn’t run the Distribution Wizard or something wrong happened while the Distribution Wizard run, leaving this page outdated. My worry is that you may have other pages in the same situation. Best is to compute the changes for all XWiki Standard pages to see what else is not up-to-date. See https://extensions.xwiki.org/xwiki/bin/view/Extension/Extension%20Manager%20Application#HChanges . Go to Extension Manager administration section, search for “flavor” and compute the changes for the “XWiki Standard Flavor”. Note that it may take a while.
Hope this helps,
Marius