Security researchers Nicholas Carlini, Adrienne Porter Felt, and Prateek Saxena reviewed 50 popular and 50 random Chrome extensions from the official Chrome Web Store for security vulnerabilities and discovered that 27 of the 100 extensions “leak all of their privileges to a web or WiFi attacker”. These 27 extensions account for a total of 51 vulnerabilities. Seven of the vulnerable extensions have more than 300k users each according to data provided by the Chrome Web store.
50 popular extensions... I'll bet that I use quite a few of those popular extensions. Now if only I knew what those 50 popular extensions were. Another thing to think about before installing loads of extensions I guess.
Rest of the article: http://www.ghacks.net/2011/10/12/27-out-of-100-chrome-extensions-insecure/