1635017 - Websites can detect private windows

Status: RESOLVED DUPLICATE of bug 1366318

(Firefox :: Private Browsing, defect)

Description

[Gregg Tavares]

Attachment: Screen Shot 2020-05-04 at 15.09.06.png

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.129 Safari/537.36

Steps to reproduce:

Went to a vanity fair article in a private window like this one

https://www.vanityfair.com/hollywood/2020/05/little-gold-men-network-rewatch

See screenshot

Actual results:

Scrolling down a few moments later a popup appeared saying effectively "you can't be private on this site". Took about 12 seconds

Also happens on 77.0a1 (2020-05-03)

Expected results:

The site should not have been able to detect private mode

Note: this also happens on Chrome but not on Safari

Comment 1

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

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Comment 2

[Francesco Lodolo [:flod]]

Duping against a meta bug seems counterintuitive, in case feel free to change.