This is a great example of online companies using third party plug-ins
"Recently, my mom was browsing for a new pair of glasses, and upon visiting marveloptics.com, her antivirus software started flashing alerts over some malicious javascript. Always curious to see how real-world attacks work, I reverse engineered it."
~Jesse Li~
https://blog.jse.li/posts/marveloptics-malware/
(And in case you're wondering, yes, the malware is still being served up)