When using a UDP ports in Workstation (eg VoIP in customized Windows) is a chance to leak sensitive information? Or Whonix firewall simply does not pass traffic in UDP ports?
This is a complex question. System DNS is UDP and resolved by Tor’s DnsPort (unless transparent WORKSTATION_TRANSPARENT_DNS get disabled). Other UDP traffic is filtered (unless encapsulated into a TCP stream, such as a VPN tunnel). UDP according to leak tests, doesn’t leak.
Voip clients however, can cause other issues with respect to anonymity/privacy/security unrelated to firewall leaks [protocol leaks], for example, see Skype: