> Yes, this is accurate - extensions cannot intercept requests from PDFium. PDFium, in Chrome, is (partially) implemented as a component extension, and extension requests cannot be monitored or manipulated by other extensions. The behavior of protecting component extension requests is critical for security reasons, and we are unlikely to change it.
Ug, not exactly sure what triggers PDFium vs PDF download, but this is especially bad if I could load a PDF in an iframe and get around any of your ad blocking. I also question why it's considered an extension at the user level. Anything installed and enabled by default should be considered part of the core browser and not an extension (regardless of the mechanisms, such as the extension one, they are implemented with). I understand the levels of separation and implementation difficulty fixing this entails, I really do, but the practicalities of your on-by-default PDF renderer making web requests different than a web page is too bad to ignore.
This goes to show that you can not count on extensions to filter web requests in your browser. You must do it at the network level or have a dedicated browser for it (e.g. Tor Browser). Unfortunately it's often extensions that have all the contextual information needed to make the decisions you want.
0 - https://bugs.chromium.org/p/chromium/issues/detail?id=824705...