Chrome extensions secretly copying user data, injecting ads into pages, or mining cryptocurrency in the background have become all too common. In October of last year, Google laid out its plans to make extensions safer, which included future changes to APIs. As it turns out, those changes may prevent most content blockers from working.
Chrome extensions use a certain manifest version that determines what APIs they can and cannot use — similar to how Android applications target a specific Android API level. The current manifest version, v2, was introduced in 2012. Manifest v3 is currently under development, and will include several breaking changes to APIs, including one that affects content blockers.
Raymond Hill, the developer behind uBlock Origin and uMatrix, explained in the Chromium bug tracker that one of the changes in Manifest v3 would break complex content filtering: