Scriptlet to spoof CSS property value

[MasterKia]

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 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

What about a scriptlet that will return a different CSS property value to counter getComputedStyle() (maybe by proxying CSSStyleDeclaration.prototype.getPropertyValue) to foil sophisticated anti-blockers that check all CSS properties of an element (like megaup, aternos, ylilauta.org)?

example.com##+js(spoof-css, a[href*="ads/redirect/"] > img, clip-path, none)
example.com##a[href*="ads/redirect/"] > img:style(clip-path: circle(0) !important;)

A specific URL where the issue occurs.

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Steps to Reproduce

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Expected behavior

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Actual behavior

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uBO version

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Browser name and version

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Operating System and version

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[krystian3w]

Why not:

example.com##a[href*="ads/redirect/"] > img:spoof(clip-path: none !important;)
example.com##a[href*="ads/redirect/"] > img:style(clip-path: circle(0) !important;)

Based on migration ra, rc to pseudo-classes syntax.

[MasterKia]

Nice idea. My only concern is that we might experience the same problem with ##body:remove-attr(oncontextmenu) sometimes not working on Chromium.

[krystian3w]

I suppose this trouble can only apply to javascript written with html attributes:

https://www.w3schools.com/tags/ref_eventattributes.asp

which is not recommended - actions should be created in the file or "<script> </script>" section (https://kornel-ski.translate.goog/pl/onclick?_x_tr_sl=pl&_x_tr_tl=en&_x_tr_hl=pl&_x_tr_pto=wapp).

[uBlock-user]

##body:remove-attr(oncontextmenu)

Use ##body:remove-attr(oncontextmenu):watch-attr(oncontextmenu) then.

[krystian3w]

#2618 (comment) - This solve trouble with blocked right click on 99% of pages?

#2403 (comment)

[gorhill]

Based on migration ra, rc to pseudo-classes syntax.

Spoofing requires to patch JavaScript calls, which can only be done in the page world. Code for procedural cosmetic filters execute in content script world.

[krystian3w]

And are there any plans to e.g. on musixmatch.com replace +js(ra, oncontextmenu, body, complete) to +js(nowoif, something)?

https://github.com/uBlockOrigin/uAssets/blob/ee4ce452e50fccf8253a6014db44122f4faf5e38/filters/annoyances.txt#L2007

[gorhill]

Can I get real world examples (preferably not requiring account) for which I can test such scriptlet?

[peace2000]

Can I get real world examples (preferably not requiring account) for which I can test such scriptlet?

https://ylilauta.org/jorma/131700539

To spoof that ##iframe.a has value display: block even if it's truly hidden?

[gorhill]

When I use ##iframe.a, the frame is not hidden, is there an exception filter? If so I am not seeing it in the logger.

---

Ok never mind, code stepping I see an exception filter, not reported in logger. It works if I use ##iframe.a.a.

[MasterKia]

On soft98.ir when I only add:
soft98.ir##+js(spoof-css, a[href*="s0ft98.ir"], clip-path, none) or
soft98.ir##+js(spoof-css, a[href*="s0ft98.ir"], nonsense, none)

I get detection after a few seconds.

But if I use this userscript:

// @run-at      document-start

(function () {
'use strict';
const handler = {
  apply(target, thisArg, args) {
    let response = Reflect.apply(target, thisArg, args);
    if (args == "clip-path" || args == "clipPath") {
      response = "none";
    }
    return response;
  }
}

const myProxy = new Proxy(CSSStyleDeclaration.prototype.getPropertyValue, handler);
CSSStyleDeclaration.prototype.getPropertyValue = myProxy;

}) ();

and then use this filter:
soft98.ir##a[href*="s0ft98.ir"]:style(clip-path: circle(0) !important;)

Then I get no detection.

Edit: added @run-at.

[gorhill]

But if I use this userscript:

I tried with ViolentMonkey and I still get detection with your script.

---

Ok, seems to work when using // @run-at document-start.

[gorhill]

Note that your code has an issue but it accidentally works because of truthiness. Should be:

if (args[0] === "clip-path" || args[0] === "clipPath") {