Various embodiments enable detection of third party content sources that may pose a privacy risk to a user. In at least some embodiments, webpages navigated to via a browser can be processed to identify third party content sources that provide content for the webpages. Data may be stored to relate the third party content sources to webpages in which the third party content is encountered. The data may then be analyzed to determine when a particular third party is in a position to observe browsing habits of a user. Responsive to determining a privacy risk, notification may be output in a variety of ways to inform a user of potentially risky content. In at least some other embodiments, notification can be made by way of a user interface instrumentality that is automatically presented to a user to inform the user of a potentially risky third party content source.