Security issue on Thunderbird made by Avast

[REDACTED]

On Vista Home Premium french SP2, Thunderbird 45.2.0, the update of Avast to V 12.1.2272 makes a security issue on Thunderbird (TB) :

When, in TB, I clic on "Courrier entrant" folder (Incoming messages) of each of my accounts to see my messages, a TB windows tells  "ajout d'une exception de sécurité" (add of a security exception), and the certificate emitted by Avast is invalid (see attachment).

I have to accept (with clic on "not permently") this security exception to see my messages

This problem is always present in Avast 12.3.2280.

Is another user having the same problem ?

[Asyn]

I have to accept (with clic on "not permently") this security exception to see my messages

Allow it and you should be good to go.

[REDACTED]

Thanks for your fast response.
But are you sure that to do what you says is not dangerous (for a security point of view) ?

[Asyn]

But are you sure that to do what you says is not dangerous (for a security point of view) ?

Yep.

[DavidR]

Whilst this probably won't make any difference, but the latest TB version is Thunderbird 45.3.0.