Bug 303118 – DNR rules are not applied to a private window if Safari opens with a non-private window and vice versa

• Component: WebKit Extensions
• Status: NEW

[Jeff Johnson]

Created attachment 477519 [details]
Sample Xcode project demonstrating the bug

Safari 26.1 on macOS 15.7.2

DeclarativeNetRequest rules are not applied to private windows if "Safari opens with: A new window" in Settings. Alternatively, they're not applied to non-private windows if "Safari opens with: A new private window" in settings.

This might be the same bug, or a related bug to https://bugs.webkit.org/show_bug.cgi?id=290256 DeclarativeNetRequest rules are not applied to a new default profile window in some circumstances

Steps to reproduce:
1) Open Safari General Settings
2) Safari opens with: A new window
3) Unzip, build, run, and enable the attached Safari extension DNRProfilesBug
4) Quit Safari
5) Open Safari
6) Open https://gs.statcounter.com/detect in the current window
7) Verify that the User-Agent is "My Custom User Agent"
8) Open a new private window
9) Open https://gs.statcounter.com/detect in the new private window

Expected results: User-Agent is "My Custom User Agent"

Actual results: User-Agent is Safari

You can open the extension popup window to verify that the DeclarativeNetRequest rules are still set to customize the User-Agent, even though the rules aren't currently effective in the tab.

This bug breaks my Safari extension ChangeTheHeaders: https://apps.apple.com/app/changetheheaders-for-safari/id6743129567

[Radar WebKit Bug Importer]

<rdar://problem/165419520>

[Jeff Johnson]

I received a bug report from a customer showing that DNR rules are broken in other circumstances too, in non-private windows even when Safari opens with a non-private window. I haven't found steps to reproduce for that, but it may involve having Safari content blockers installed. I've just reported what I can reproduce.

[Jeff Johnson]

This bug is also reproducible on iPadOS 26.1

[Brian Weinstein]

Thank you for filing this Jeff!

I believe this was fixed by:
https://bugs.webkit.org/show_bug.cgi?id=301720

Is it possible to test with the latest Safari Technology Preview on Mac to confirm?

[Jeff Johnson]

(In reply to Brian Weinstein from comment #4)
> Thank you for filing this Jeff!
> 
> I believe this was fixed by:
> https://bugs.webkit.org/show_bug.cgi?id=301720
> 
> Is it possible to test with the latest Safari Technology Preview on Mac to
> confirm?

This bug does indeed appear to be fixed in Safari Technology Preview 233. Thanks!