At least on firefox, this can be changed through the preference security.cert_pinning.enforcement_level (see https://wiki.mozilla.org/SecurityEngineering/Public

At least on firefox, this can be changed through the preference security.cert_pinning.enforcement_level (see https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinning https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinn...).