User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:93.0) Gecko/20100101 Firefox/93.0

Steps to reproduce:

When iframe response contains header x-frame-options: ALLOWALL (invalid value according to https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options) frame selector icon in devtools top bar disappears.

Version Nightly 93.0a1 (2021-08-29) (64-bit)

Steps to reproduce:

1. Open page console
2. Go to https://jsfiddle.net/
3. Make sure, frame selector icon is present
4. Press Ctrl+Enter to render an (empty) snippet

Actual results:

Frame selector icon is gone. Console contains error message

Invalid X-Frame-Options header was found when loading “https://fiddle.jshell.net/_display/?editor_console=true”: “ALLOWALL” is not a valid directive. _display

Expected results:

Error message is printed, but frame selector is still present and work.

In the current released version 91.0.1 (64-bit) the icon remains preset, but the frame context is not switched - it gets stuck on the root frame.

The Bugbug bot thinks this bug should belong to the 'DevTools::Console' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

Jakub, could you go to about:config and check the value of the fission.autostart pref? I supposed it's set to true.

I can reproduce the issue when it is true (i.e. Fission is enabled)
When opening jsfiddle, the location of the iframe in which the "result" is displayed is about:blank, which is displayed by the iframe picker.
But when running the fiddle, the iframe location changes to fiddle.jshell.net, a remote origin, which is known to be not displayed in the iframe picker when fission is enabled (See Bug 1608054).

Let us know if the fission.autostart isn't set to true, which would mean it's another issue

Thanks for checking Nicolas, removing my ni?

Hi Nicolas, yes fission.autostart pref is set to true.

(In reply to Nicolas Chevobbe [:nchevobbe] from comment #2)

Jakub, could you go to about:config and check the value of the fission.autostart pref? I supposed it's set to true.

I can reproduce the issue when it is true (i.e. Fission is enabled)
When opening jsfiddle, the location of the iframe in which the "result" is displayed is about:blank, which is displayed by the iframe picker.
But when running the fiddle, the iframe location changes to fiddle.jshell.net, a remote origin, which is known to be not displayed in the iframe picker when fission is enabled (See Bug 1608054).

Let us know if the fission.autostart isn't set to true, which would mean it's another issue

Jakub, I think you forgot to add your comment :)

I shouldn't write anything before having a cup of coffee.
Thanks for checking Jakub.

So I'm going to make this bug a duplicate of Bug 1608054. We're currently working on this bug, so hopefully it will be fixed in Firefox 95. In the meantime, if this is a blocker for you, you can set the pref to false and restart Firefox, this should fix the issue.