uBO Icon Blank White and sometimes blinks while page loads on Firefox when 'privacy.resistFingerprinting' = true

[jjohns71]

Prerequisites

• I verified that this is not a filter issue
  • Filter issues MUST be reported at filter issue tracker
• This is not a support issue or a question
  • Support issues and questions are handled at /r/uBlockOrigin
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue
  • Your issue may already be reported.
• I tried to reproduce the issue when...
  • uBlock Origin is the only extension
  • uBlock Origin with default lists/settings
  • using a new, unmodified browser profile
• I am running the latest version of uBlock Origin
• I checked the documentation to understand that the issue I report is not a normal behavior

Description

When Firefox setting privacy.resistFingerprinting is set to 'true' in about:config, the uBO icon shows up as a white block. When a page is being loaded it sometimes flashes between the white block and the standard uBO icon.

When Firefox setting privacy.resistFingerprinting is set to 'false' there appears to be no issue. I believe this issue only started happening with the last 2 beta releases. (1.16.5b2 & 1.16.5b3)

Demo gif is below:

A specific URL where the issue occurs

https://github.com/uBlockOrigin/uBlock-issues

Steps to Reproduce

1. Enable 'privacy.resistFingerprinting' to true in 'about:config' firefox options
2. Close and relaunch Firefox and observe the uBO icon is now a white box that sometimes flashes on page loads.

Expected behavior:

uBO icon shows as normal.

Actual behavior:

uBO icon is white block.

Your environment

• uBlock Origin version: 1.16.5b3
• Browser Name and version: Firefox 59.0.3 (64 bit)
• Operating System and version: Windows 10

[uBlock-user]

Can't reproduce on Nightly.

[jjohns71]

After setting privacy.resistFingerprinting to true did you close Firefox and reopen? I guess it could be an issue fixed in beta/nightly builds if so. If that is the case, it is a bit odd that it just started happening with 1.16.5b2 and not in previous builds though.

[uBlock-user]

I'm able to reproduce it on the stable, it doesn't flicker but the icon turns into a white block when visiting the aformentioned URL

[jjohns71]

FYI: For me it is white block everywhere, not just the posted link.

Also, the flickering I described happens one time toward the end of the posted example gif after clicking on 'Features' link in the gif.

[uBlock-user]

Yes, it happens everywhere on Stable, although no flickering on my end. Probably a regression in the dev build.

[gorhill]

Browser console reports:

Blocked moz-extension://7a490fe4-6765-4415-95a1-925dc0e4e333/background.html in page moz-extension://7a490fe4-6765-4415-95a1-925dc0e4e333/background.html from extracting canvas data because no user input was detected. moz-extension://7a490fe4-6765-4415-95a1-925dc0e4e333/js/vapi-background.js:689.

uBO now uses canvas to generate the icon image data once which it then uses and reuses afterward. Apparently resistFingerprinting gets in the way of using canvas.

[uBlock-user]

So it's specific to Stable version as that doesn't appear to be happening to Nightly ?

[gorhill]

So it's specific to Stable version as that doesn't appear to be happening to Nightly ?

Can this be confirmed? I use Nightly as my main browser, I try to not mess with it's current settings. If this works fine in Nightly, this means there is an issue somewhere in bugzilla about this. In any case, I could peek a pixel in the image data returned to find out whether the data is valid, and abort using image data if not.

[uBlock-user]

Yes, I did confirm it. It doesn't happen on Nightly and works as expected with Fingerprinting switch enabled.

[gwarser]

https://bugzilla.mozilla.org/show_bug.cgi?id=1453916
https://bugzilla.mozilla.org/show_bug.cgi?id=1412418
mozilla-services/screenshots#3691
https://bugzilla.mozilla.org/show_bug.cgi?id=1412961

[uBlock-user]

According to the last one listed, it's fixed in v61.