[jitsi-users] Verify Certificate error, need help

jitsi 2.2.4603.9615
on linux
was working fine for some time, untill recently:,
the problem:

ok, when changing status from offline to online, jitsi generates the following error:

Jitsi can't verify the identity of the server when connecting to [jit.si, _xmpp-client.jit.si]. The certificate is not trusted, which means that the server's identity cannot be automatically verified. Do you want to continue connecting? For more information, click "Show Certificate".

This looks like potential security threat.
How to resolve it ?