[tbb-bugs] #18218 [Applications/Tor Browser]: The certificate is not trusted because the issuer certificate is unknown. (Error code: sec_error_unknown_issuer)

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#18218: The certificate is not trusted because the issuer certificate is unknown.
(Error code: sec_error_unknown_issuer)
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 Reporter:  bugzilla                  |          Owner:  tbb-team
     Type:  defect                    |         Status:  new
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  tbb-usability-website     |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Comment (by cypherpunks):

 Because of the bug in Firefox, Tor Browser can fall into undesirable
 state, preventing browsing of certain sites, e.g.
 https://observatory.mozilla.org/analyze/msdn.microsoft.com states that
 > HTTP Strict Transport Security (HSTS) header cannot be set, as site
 contains an invalid certificate chain
 but when it is set anyway, Tor Browser shows
 > Your connection is not secure
 > The owner of msdn.microsoft.com has configured their website improperly.
 To protect your information from being stolen, Tor Browser has not
 connected to this website.
 > This site uses HTTP Strict Transport Security (HSTS) to specify that Tor
 Browser may only connect to it securely. As a result, it is not possible
 to add an exception for this certificate.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/18218#comment:6>
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