That's really clever! Fixes the "silently" part at least, though given that most applications typically require frequent updates and that this doesn't prevent targeted attacks, I'm not sure how useful it is in practice, at least for mainstream applications.
Signed web bundles with binary transparency and independent review would be far superior, if they actually existed. (Which sadly, they don't right now.)
Thanks! Automatic updates are still possible; you can implement a code signing-based flow on top of this, or fetch hashes from GitHub releases, or anything, really. Attacks are only possible during setup, and targeting at that point in time is difficult because the client won't have authenticated yet. Anything else (attacks that rely on clearing the local state) can be mitigated using careful UI design.
The big problem with transparency logs is that they can't prevent attacks in real time because of the merge delay. You'll only find out afterwards if you've been attacked. It significantly raises the bar for an attack, but can't stop one from happening.
Signed web bundles with binary transparency and independent review would be far superior, if they actually existed. (Which sadly, they don't right now.)