[tbb-bugs] #25735 [Applications/Tor Browser]: Tor Browser stalls while loading Facebook login page (Waiting for static.xx.fbcdn.net)

[Tor Bug Tracker & Wiki]

#25735: Tor Browser stalls while loading Facebook login page (Waiting for
static.xx.fbcdn.net)
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     Reporter:  uzi                       |      Owner:  tbb-team
         Type:  defect                    |     Status:  new
     Priority:  Medium                    |  Milestone:
    Component:  Applications/Tor Browser  |    Version:
     Severity:  Major                     |   Keywords:
Actual Points:                            |  Parent ID:
       Points:                            |   Reviewer:
      Sponsor:                            |
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 Problem:
 After opening the Tor Browser and typing in facebook.com, page loading
 hangs, status bar showing "Waiting for static.xx.fbcdn.net"

 HTTP GET requests for small images from static.xx.fbcdn.net stall in the
 "Blocked" state for minutes - viewed in Developer tools / Network /
 request / Timing (see attached screenshot Step2.png).

 When a different website is opened in a new tab, HTTP requests continue
 loading successfully - seems to be some livelock within the browser.

 This is **not a network issue**, connectivity in the browser works fine,
 also verifed without a SOCKS proxy (direct connection without Tor).

 Reproducibility: nearly 100%

 Environment:
 - Windows 10 Pro, 64bit
 - Tor Browser 7.5.3 for Windows, english
 - Tor Browser 8.0a5 for Windows, english

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25735>
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