Cosmetic filters and scriptlets don't get injected for an iframed website

[uBlock-user]

Description

As above and discussed internally at https://github.com/orgs/uBlockOrigin/teams/ublock-issues-volunteers/discussions/177

A specific URL where the issue occurs

https://www.underhentai.net/shujii-no-inbou/

Steps to Reproduce

• Open the logger, browse to https://www.underhentai.net/shujii-no-inbou/ (NSFW) in a new tab

• Scroll down abit untill the episode listing appears.

• Click the watch button for the first episode under Online category and be led to https://www.underhentai.net/watch/?id=1790&ep=0

• Switch to the logger page, put streamz. as the filter, observe that scriptlets are not listed by the logger even though uBO is injecting 3 scriptlets as per uBlock Filters list --

streamz.cc##+js(acis, Math, zfgloaded)
streamz.cc##+js(window.open-defuser)
streamz.cc##+js(set, jQuery.adblock, false)

Cosmetic filters are not injected themselves, to reproduce, add streamz.cc###video_1 and refresh the page, player will still appear working even though it's supposed to be hidden with the above filter.

Expected behavior:

Scriptlets applied to an iframed domain appear as expected.

Actual behavior:

Scriptlets applied to an iframed domain do not appear.

Your environment

• uBlock Origin version: 1.25.3rc0
• Browser Name and version: Firefox 76
• Operating System and version: Win 10

[gorhill]

So far from what I can tell is that uBO's content scripts are not injected by Firefox, this would explain why either cosmetic filtering or scriptlets are not injected, so the logger is reflecting this correctly.

I don't know why Firefox is not injecting uBO's content scripts -- I wonder if this has to do with the streamz.cc iframe having a sandbox attribute set, this needs further investigation.

[gorhill]

There is https://bugzilla.mozilla.org/show_bug.cgi?id=1610394, which has been marked as a duplicate of https://bugzilla.mozilla.org/show_bug.cgi?id=1411641.

[MasterKia]

uBlockOrigin/uAssets#16138

Cosmetic filters don't work on the iframe (with sandbox attribute) inside this page:
https://inyheter.no/2022/12/27/disse-lovene-trer-i-kraft-ved-nyttar/

inyheter.no##.wp-embed-comments
inyheter.no##.wp-embed-share

I've found two workarounds:

1. Use HTML filters:

inyheter.no##^.wp-embed-comments
inyheter.no##^.wp-embed-share

2. Remove the sandbox attribute:
   Add inyheter.no##iframe:remove-attr(sandbox), go to the page and right-click on the frame and choose This frame => Reload frame, now all cosmetic filters will work on the iframe; bad for security.