“Some highly-ranked online tools for editing or “cleaning” HTML seem to be secretly injecting links into their output to push themselves and affiliated sites up the search engine rankings.”
Paste your article into a free HTML cleaner and it quietly plants a backlink to someone else’s site. BoingBoing, the German Football Association and a Kaspersky piece on staying safe from hackers all got hit. Google’s algorithm rewarded the scam with the top spot. It took a guy with two glasses of wine and an Ahrefs subscription to notice.