What WebRTC can expose
Browsers use WebRTC to establish direct audio, video, and data connections. During that process, an ICE candidate can contain an address that the browser believes another peer may use to reach it.
Modern browsers commonly mask local addresses with mDNS hostnames. A public candidate may still appear when a STUN server reports the public address associated with the connection.
When it becomes an IP leak
A public WebRTC address is meaningful when it differs from the public address observed through the website connection. If a VPN is active, that difference can indicate that WebRTC discovered a public address outside the VPN tunnel.
Private addresses, loopback addresses, and mDNS hostnames are local network identifiers. Deep IP Trace displays them as evidence but does not classify them as public IP leaks.
Why browser results differ
WebRTC behavior depends on the browser, operating system, network configuration, extensions, and VPN client. One browser may return only mDNS identifiers while another exposes a server-reflexive public address on the same device.