Capital One Shopping monitors the products you view and purchase on e-commerce sites in order to notify you when savings are available for those products across various retailers, and to in turn update other Capital One Shopping users on the latest prices available for products they've viewed or purchased.
Additionally, Capital One Shopping monitors successful coupon codes found by Capital One Shoppers - “the community” - which are then shared and contribute to finding savings for others.
Related to permissions, the Capital One Shopping extension requires these in order to display notifications in your browser window when better prices are found, coupons are tested, or when Capital One Shopping Rewards are available. Other Chrome extensions which require similar permissions include the Amazon, Microsoft Office Online, Google Calendar, Evernote, Pocket, and Pinterest extensions. Like Capital One Shopping, these extensions must have the ability to interact with data in web pages (not simply view the data) to work properly.