1840363 - The canvas signature reported in https://browserleaks.com/canvas changes after a refresh

Status: NEW

(Core :: Graphics: Canvas2D, defect, P2)

Description

[Tim Huang[:timhuang]]

STR:

1. Open a tab to load https://browserleaks.com/canvas
2. Check the signature field
3. Refresh the page via the refresh icon
4. Check the Signature field

Expected result:

The signature should remain the same as in step 2.

Actual result:

The signature changes.

Chrome and Safari don't have this problem.

After running a mozregression, this push causes this issue.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1779227

:jfkthame, since you are the author of the regressor, bug 1779227, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

Set release status flags based on info from the regressing bug 1779227

Comment 3

[Timothy Nikkel (:tnikkel)]

Is there a reason why this is undesirable behaviour? Seems like reducing the ability to fingerprint via canvas would be a good thing?

Comment 4

[Jonathan Kew [:jfkthame]]

I don't see that it's particularly undesirable in principle, but it does seem surprising, and might indicate an underlying problem of some kind.

Looking (with magnification) at the images shown in the "Image File Details" field of the browserleaks page, it seems that some of the glyphs in the canvas get positioned slightly differently (a 1px offset, probably) between the initial-load rendering and the re-rendering when refreshing the page. At this point, I can't see why that should happen, and I think it'd be good to understand the cause so we can decide whether it's actually important or not.