no-large-media has no effect on images loaded through 3p CSS

[emanruse]

Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• The issue is not present after disabling uBO in the browser.
• I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• uBO is the only extension.
• uBO uses default lists and settings.
• using a new, unmodified browser profile.

Description

no-large-media has no effect when CSS is blocked but 3p for the domain is noop

A specific URL where the issue occurs.

https://github.com

Steps to Reproduce

1. Use the following settings

{
  "version": "1.55.0",
  "userSettings": {
    "externalLists": "",
    "firewallPaneMinimized": false,
    "importedLists": []
  },
  "selectedFilterLists": [
    "user-filters"
  ],
  "hiddenSettings": {},
  "whitelist": [
    "about-scheme",
    "moz-extension-scheme"
  ],
  "dynamicFilteringString": "* * * block\n* * inline-script block\n* * 1p-script block\n* * 3p-script block\n* * 3p-frame block\n* * image block\n* * 3p block\nbehind-the-scene * * block\ngithub.com * * noop\ngithub.com * 3p noop",
  "urlFilteringString": "",
  "hostnameSwitchesString": "no-popups: * true\nno-remote-fonts: * true\nno-large-media: * true\nno-csp-reports: * true\nno-scripting: * true",
  "userFilters": "*$stylesheet\n*$document,csp=style-src\n"
}

*The value for "Block media elements larger than" is 0 KB.

2. Open uBO's logger
3. Visit e.g. https://github.com

Expected behavior

Images > 0 KB should not be loaded.

Actual behavior

Images are loaded.

uBO version

1.55

Browser name and version

Tor Browser 13.0.9 (based on Firefox 115.7.0esr)

Operating System and version

Whonix 17

[gwarser]

Are you sure they are not loaded from cache?

This is on ESR with your settings imported + 0kB large media. Also tried with advanced settings enabled and it's fine.

Also fine in Tor Browser 13.0.9.

[emanruse]

Are you sure they are not loaded from cache?

Absolutely sure. Tested in a clean VM in which a browser was never run. Additionally tested explicitly by looking at the web console with network caching disabled. Both web console and uBO's console show both the blocked and the non-blocked requests.

[stephenhawk8054]

My console shows all images being blocked:

[gorhill]

Tested in a clean VM in which a browser was never run.

Did you try reloading the page with cache bypass after you setup your config?

[gwarser]

Ok, there is some inconsistency between uBO logger and dev console

[emanruse]

Did you try reloading the page with cache bypass after you setup your config?

Yes. Many times. Strangely, as I am retrying right now (another clean setup), images appear blocked. I absolutely sure I am doing the same as before. Very strange.

[emanruse]

@garry-ut99 At the time I reported this, I was getting case1 + case2 simultaneously. As per my previous reply and as of today (updated to uBO 1.56 and TB 3.0.10), I am getting only case 1.

Another thing/issue, maybe related or not, is that after disabling no-large-element, and reloading site, then enabling no-large-element again and reloading site again, no images are blocked anymore, even with cache cleared and disabled in dev console

That's it! It might have been this which I have observed initially and I can reproduce it today too. *Please note that when you edit a comment, I don't get email notification about it.

[uBlock-user]

I can consistently reproduce images not getting blocked despite Block media elements setting set to 0 KB on Firefox 124

[gorhill]

there is some inconsistency between uBO logger and dev console

no-large-media blocks after response headers are received since that feature needs response headers to find out the response size.

[gorhill]

For every "images not blocked" instance, I need to know how exactly this was determined: visual? uBO's logger? browser network pane?

[uBlock-user]

uBO's logger

Yes

browser network pane?

Yes

On my side profile picture image also loads (tested at https://github.com/uBlock-user)

Content-Length header is also present as per the above image.

[gorhill]

OP's repro steps didn't mention disabling no-large-media.

[emanruse]

OP's repro steps didn't mention disabling `no-large-media`.

Yes. The reason is probably that I made many tests and I blindly trusted the fact that disabling cache works as expected, i.e. I didn't expect that the issue is more complex, as it turned out. Sorry for the confusion. I confirmed the actual finding of @garry-ut99 though, so he helped to clarify that. Thanks.

[stephenhawk8054]

@progman-dt Which sites did you use to test?

[progman-dt]

@progman-dt Which sites did you use to test?

habr.com

[stephenhawk8054]

The font network is blocked correctly for me

[progman-dt]

OMG, I'm so sorry for the false alarm! Looks like one of my regional filters has an override for google font domains 🤦

[stephenhawk8054]

You can use badfilter to disable the allowed-filter. For example

@@||fonts.gstatic.com^$badfilter