An analysis of a popular Google Chrome ad block extension for YouTube has uncovered the ability to execute arbitrary JavaScript code. According to Island, the extension, named Adblock for YouTube, has more than 10 million installs and carries a Featured badge on the Chrome Web Store. The extension (ID: cmedhionkhpnakcndndgjdbohmhepckk) description states that it allows users to prevent web page elements like ads, including preroll ads, from being displayed on the video sharing platform, as well as on external sites that load YouTube. While the add-on offers the promised functionality, it also features capabilities to run arbitrary JavaScript code. "It also contains the architectural ingredients for arbitrary JavaScript execution on any website, activated by a single server-side…