An anonymous reader writes "Ars reports that the developers of moderately popular Chrome extensions are being contacted and offered thousands of dollars to sell ownership of those extensions. The buyers are then adding adware and malware to the extensions and letting the auto-update roll it out to end users. The article says, 'When Tweet This Page started spewing ads and malware into my browser, the only initial sign was that ads on the Internet had suddenly become much more intrusive, and many auto-played sound. The extension only started injecting ads a few days after it was installed in an attempt to make it more difficult to detect. After a while, Google search became useless, because every link would redirect to some other webpage. My initial thought was to take an inventory of every program I had installed recently—I never suspected an update would bring in malware. I ran a ton of malware/virus scanners, and they all found nothing. I was only clued into the fact that Chrome was the culprit because the same thing started happening on my Chromebook—if I didn't notice that, the next step would have probably been a full wipe of my computer.'"