This Chrome extension installed without my knowledge and defied many attempts to get rid of it. For one, it hijacked my image search tab. Reset Chrome, ran Emsisoft, M-Bam, and Superantispyware scans. M-BAM showed PUPS and quarantined them but no other scans turned anything up. Restarted my computer and it appears to be gone. I am careful surfing so not sure where I got it. Have adware blockers but had to disable them for Weatherunderground, which is full of adds. How do I permanently stop this from reappearing?