docs.google.com: element picker/zapper causes error popup

[vrad-exe]

Prerequisites

• This is NOT a YouTube, Facebook, Twitch or a shortener/hosting site report. These sites MUST be reported by clicking their respective links.
• I read and understand the policy about what is a valid filter issue.
• I verified that this issue is not a duplicate. (Use this button to find out.). Comment in the old issue threads even when they are closed or even if you have a different problem.
• I did not remove any of the default filter lists, or I have verified that the issue was not caused by removing any of the default lists.
• I did not enable additional or non-default filter lists, or I have verified that the issue still occurs without enabling additional filter lists.
• I do not have custom filters/rules, or I have verified that the issue still occurs without custom filters/rules.
• I have verified that the web browser's built-in content blocker/tracking protection, network wide/DNS blocking, or my VPN is not causing the issue.
• I have turned off all other extensions and the issue still persists. (exception "Firefox Multi-Account Containers").
• If this is about a breakage or detection, I have verified that it is caused by uBlock Origin and isn't a site or browser issue.
• I have verified that the browser I am using is up to date with no pending updates.
• I did not answer truthfully to ALL the above checkboxes.

URL address of the web page

https://docs.google.com/document/d/13YsANvWL36l7v0bKKm4uAPhpDXnHJXrluYoQRWxP_ts/edit?tab=t.0

Category

breakage

Description

On Google Docs when attempting to use the element picker or zapper, a dialog saying that "an error occurred" will pop up. Sometimes it's inconsistent but will usually appear after a few tries. Clicking on an element will make another duplicate copy of the dialog pop up and this will repeat whenever the uBO element block dialog is interacted with.

I couldn't seem to reproduce this when using another window/profile, but it persistently happened in my main profile even after turning off all other extensions, firefox tracking protection, custom filters and filter lists, etc.

Browser name and version

Firefox 146.0 (latest version as of writing)

Other extensions used

A lot, usually:

Full extension list (image got squished for some reason???)

However I tested this with all extensions besides uBO disabled and the issue persisted.

Country

US

Screenshot(s)

Screenshot(s)

Configuration

Details

uBlock Origin: 1.68.0
Firefox: 146
filterset (summary):
 network: 161662
 cosmetic: 47046
 scriptlet: 24115
 html: 2658
listset (total-discarded, last-updated):
 added:
  https://raw.github.com/reek/anti-adblock-killer/master/anti-adblock-killer-filters.txt: 0-0, 31m
  https://raw.githubusercontent.com/laylavish/uBlockOrigin-HUGE-AI-Blocklist/main/list.txt: 4999-42, 31m
 default:
  user-filters: 146-7, never
  ublock-filters: 42119-69, 21m Δ
  ublock-badware: 10575-32, 21m Δ
  ublock-privacy: 3553-2, 21m Δ
  ublock-unbreak: 2774-1, 21m Δ
  ublock-quick-fixes: 409-14, 21m Δ
  easylist: 82855-146, 21m Δ
  easyprivacy: 54961-28, 21m Δ
  urlhaus-1: 31070-6, 36m
  plowe-0: 3479-979, 20m
filterset (user): [array of 146 redacted]
trustedset:
 added: [array of 6 redacted]
userSettings:
 advancedUserEnabled: true
 cloudStorageEnabled: true
 largeMediaSize: 0
hiddenSettings: [none]
supportStats:
 allReadyAfter: 755 ms (selfie)
 maxAssetCacheWait: 45 ms
 cacheBackend: indexedDB
popupPanel:
 blocked: 36
 network:
  google.com: 24
  csp.withgoogle.com: 12
 extended:
  ##div[role="tooltip"]:has-text(Try Gemini):upward(3):remove()
  ##+js(prevent-xhr, method:POST url:/logImpressions)

[gorhill]

I couldn't seem to reproduce this when using another window/profile, but it persistently happened in my main profile

Unable to reproduce. If you can't reproduce in a new profile, then something else in your current profile is causing the issue, you will have to investigate on your side, I can't investigate what I can't reproduce, and we do ask people that issues reported here are reproducible in a new profile.

---

Is being logged in into Google required to reproduce the issue?

[vrad-exe]

Okay, after further testing the issue is somehow tied to my google account. I can sign in with that account in any firefox profile, in any container, and it will break with any google docs/sheets/slides file. But when viewing anonymously or signed into my alt account it doesn't happen. I have no idea where to go with this from here but I'd have to imagine there have to be at least some other accounts affected by this? Maybe it's some kind of A/B testing rollout?

[vrad-exe]

In my main profile/container I'm also signed into a school account, but the issue only happens when viewing the document with my personal account, and persists even when the school account is signed out entirely.

It also still happens even if ublock filtering is entirely turned off for the website but the element picker is opened anyway (by clicking the power button back on, then closing and reopening ublock without reloading the page so the element picker button appears). This is probably kind of unintended behavior but it seems worth noting because in this case no red boxes show up yet the error dialog continues to open repeatedly for every click.

[gorhill]

I logged into Google and I still could not reproduce.

When the error occurs, is there anything related to it in the dev tools console?

[vrad-exe]

Oh, there actually is an error message here that seems to be related, didn't catch this when looking in the console earlier.

Uncaught 
Object { message: 'Error in protected function: Permission denied to access property "document" on cross-origin object', cause: DOMException, F: true, stack: "", … }
m=kix_core:4165:345
    irf https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:4165
    c https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:6278
    (Async: setTimeout handler)
    c https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:4167
    AH https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:2951
    O https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_ita:319
    Zme https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:2950
    Ume https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:2950
    c https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:6278
    F https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:6278
    a https://docs.google.com/_/docs/_/js/k=docs.client_js_prod.en.C9C0rDAgV1w.es5.O/am=ABAMAAM/d=0/wt=0/rs=AGWKN8lesQMvbdkAgHwy4qNHEfF-ACd_4g/m=kix_core:2947
    startPicker moz-extension://8faa77c8-4d84-42f3-862e-62953cec0a27/js/scriptlets/epicker.js:1062
    onDialogMessage moz-extension://8faa77c8-4d84-42f3-862e-62953cec0a27/js/scriptlets/epicker.js:1159
    onmessage moz-extension://8faa77c8-4d84-42f3-862e-62953cec0a27/js/scriptlets/epicker.js:1314

(I hope nothing here is like a private account token or something?)

[gorhill]

The element picker line in the stack trace is https://github.com/gorhill/uBlock/blob/1.68.0/src/js/scriptlets/epicker.js#L1062, so apparently just calling focus() on the iframe element is causing a cascade of calls in Google's code ultimately with something throwing. At this point I have no idea, and not being able to reproduce means I can't investigate further.