Google is sending out new Google Search Console notifications to some webmasters asking them to "provide a manifest and high resolution favicon for" their web sites. I guess Google wants higher resolution favicons to show up in the Chrome browser.
Google's message reads:
Google systems have been unable to detect a high-resolution favicon for your site. Our research has shown that providing a high-resolution favicon (192x192) can increase clicks by up to 2 x in surfaces like Chrome's New Tab page or the Android home screen. Missing icons, or blurry images generated by expanding low-resolution icons, degrade the user experience and may discourage users from visiting your site again from those surfaces.
Here is a screen shot of this message from @TheRealpmac:
No, don't worry, your search rankings won't dive if you get this message or have a low-resolution favicon.
Forum discussion at Twitter.