Weird Window Alert when Saving Sitemap Property Changes

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In C5 5.6.3.1 there is a weird windows alert that pops up when saving property changes in the sitemap (full and flat). One of the alerts says

The page at (domain name) says

{"rel":"SITEMAP","name":"Test","cID":"123"}<embed id="embed_npwlo" type="application/npwlo" height="0">


Might happen else where but that is where I've noticed it.I know it happens in Chrome, haven't tried other browsers yet. This happens even with a completely fresh install with nothing changed or added.

Anyone else noticing this? Any thoughts?