When you install an extension, it can request permissions that allow it to read or modify webpage content, access your tabs, observe network requests, or interact with information displayed in your browser A malicious extension can abuse those permissions to collect data from the pages you visit That could include browsing history, search queries, form data, emails, messages, or other information displayed on a webpage Now imagine you install a seemingly harmless extension You open your email If the extension has permission to access the page, it can potentially read information displayed there You visit a shopping site and enter your name, address, or other information into a form The extension can potentially access that information too You open your bank's website If it has the necessary permissions, the extension can inspect the page, interact with its content, or inject code into it Some extensions can also inject JavaScript into websites, allowing them to modify pages or monitor what happens on them Once the extension collects the information, it can send it to a server controlled by the attacker And because the extension is running inside your browser, the activity can look like normal browser behavior That's what makes malicious extensions dangerous You don't necessarily have to download malware onto your computer You can install the code yourself, give it access to your browser, and then let it sit there watching the websites you use