>source here, translated by google translate
Apparently, the error is because of the DigiCert certificate has been added to the list of trusted certificates in the system. To add, we export the certificate from Firefox:

Edit> Preferences> Advanced> Encryption> View Certificates> Authorities

We go down and select DigiCert Inc DigiCert High Assurance CA–3. We export to export the X.509 Certificate (PEM), named DigiCertHighAssuranceCA–3.crt (add the extension. crt), we can leave it in your / home.

Open a terminal and move the certificate:

$ sudo mv ~ / DigiCertHighAssuranceCA–3.crt / usr / share / ca–certificates / mozilla

Change the owner of the certificate:

$ sudo chown root: root / usr/share/ca-certificates/mozilla/DigiCertHighAssuranceCA-3.crt

Add the certificate to the list:

$ sudo dpkg–reconfigure ca–certificates

Select “Yes“, we went down and scored and accept the new certificate. From now on we no longer ask for confirmation to connect to Facebook chat. This error can also occur with Gmail and Jabber.