For static / dynamically registered content scripts, it is possible to specify whether scripts should be injected in about:blank / data:-URLs / sandboxed pages /blob:-URLs, etc.

tabs.executeScript should support the ability to run in these scripts. The tabs.executeScript API has the matchAboutBlank option, but we should probably either set this option to true by default, or introduce a new option (for context, see https://bugzilla.mozilla.org/show_bug.cgi?id=1411641#c41 and https://bugzilla.mozilla.org/show_bug.cgi?id=1475831#c16).

It may probably be easier to unconditionally set matchAboutBlank to true in the implementation of parent/ext-scripting.js, so that this code path is triggered: https://searchfox.org/mozilla-central/rev/d2f8488b6a704443a5c5bfc6d2878171b5f0d393/toolkit/components/extensions/parent/ext-tabs-base.js#791. The flag is ultimately checked at https://searchfox.org/mozilla-central/rev/d2f8488b6a704443a5c5bfc6d2878171b5f0d393/toolkit/components/extensions/WebExtensionPolicy.cpp#701-713

A unit test to check this scenario is <iframe srcdoc> and/or <iframe> (about:blank).

Depends on D133763

https://hg.mozilla.org/mozilla-central/rev/08992a56ad52

The sandbox injection depends on fixing bug 1411641.