ExtremeTech wrote an article about it but notes it's unclear what the patch does. Some sites report it adds a Windows 10 upgrade pop-up to IE11 but it appears this is not related to this patch.
Some sites are reporting that after installing the update, Internet Explorer 11 presents you with a giant “Upgrade” banner after visiting MSN.com. This is true — but it’s also not at all new. I used to use IE11 for troubleshooting and on a few websites where I needed it for compatibility reasons. The giant pop-overs that prompt users to upgrade to Windows 10 started appearing on MSN.com after Windows 10 went live, not as a result of this update.