Seeing domain blocked interstitial on Amazon.com with Chromium web embedder flag enabled

[StephenHeaps]

Description

Visiting Amazon.com in aggressive mode with the #brave-use-chromium-web-embedder flag enabled will redirect to our domain blocked interstitial (The domain blocked interstitial is only shown in aggressive mode).

Steps to reproduce

1. Enable chromium web views feature flag #brave-use-chromium-web-embedder and then relaunch the app.
2. Set to aggressive mode for Trackers & Ads Blocking in Settings > Shields & Privacy
3. Visit Amazon.com

Actual result

Blocked domain interstitial is shown:

Expected result

No interstitial shown for non-main frame navigation requests

Reproduces how often

Easily reproduced

Brave version

1.80

Device/iOS version

Affected browser versions

• latest AppStore
• latest TestFlight
• previous TestFlight

Reproducibility

• with Brave Shields disabled
• in the latest version of mobile Safari

Miscellaneous information

Internally target_frame_is_main is false:

However this value is not exposed to us to use, so we check PageTransitionIsMainFrame which instead returns true for this request so we treat it as a main frame request and show the interstitial.

Thread:
https://bravesoftware.slack.com/archives/C06UXF3KJ/p1747836136245669

[kjozwiak]

The above requires 1.80.93 or higher for 1.80.x verification 👍