Here's how I got rid of Mindspark.E, which was plaguing two pcs several times a day. I followed the directions at
https://support.eset.com/kb6551/?viewlocale=en_US
But this was not a permanent fix. I eventually deleted all Chrome extensions from my PCs. Then they were clean. Then I started adding back my extensions one at a time and running eSet. I determined that the extension OnlineMapFinder was the culprit. As soon as I added it back, I got the popup. When I removed it, rebooted, and reran eSet, everything was fine. I repeated this procedure on both PCs, and the results were identical. Then I found this link about malware from OnlineMapFinder.com
~removed link~
~removed link~