Opened 11 months ago

#31753 new defect

Web developer network tab breaks first-party isolation in some cases II

Reported by: cypherpunks Owned by: tbb-team
Priority: Medium Milestone:
Component: Applications/Tor Browser Version:
Severity: Normal Keywords: tbb-linkability
Cc: Actual Points:
Parent ID: Points:
Reviewer: Sponsor:


There are rare cases where the first-part isolation breaks if the Web developer Network tab is open. This got first reported on our blog: ​

Steps to reproduce (works in the alpha series on Windows at least):

1) Start a fresh Tor Browser and set the Torbutton log level to "3"
2) Open the Network tab in the Web developer console (Ctrl + Shift + Q)
3) Go to ​
4) Reload the page with the arrow in the URL bar


Torbutton INFO: tor SOCKS: via--unknown--:878a267349f5b487247d0a0175ae27f2

It is actually only the request for one resource that is affected. And having the Network tab open is crucial for reproducing the bug.

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