Can uBlock Origin block WebRTC?

Do you loathe online banking as much as I do? Does your bank make online banking more cumbersome each week in the name of "combating fraud" and "staying compliant" with anti-money laundering and counter terrorist financing laws?

Have you ever looked under online banking's hood? Here's an example from a bank that I use in Japan to pay for life necessities and to keep a roof over my head.

When accessing my online banking with SBI Shinsei Bank (SBI新生銀行) I noticed the following Little Snitch¹ popup:

Something in the background of the log in page tries to connect to aa.online-metrix.net on port 3478/TCP. IANA³ lists port 3478/TCP as follows:⁴

• Session Traversal Utilities for NAT (STUN) port (RFC8489)
• TURN over TCP (RFC8656)
• STUN Behavior Discovery over TCP (RFC5780)

This is what the log in screen² looks like:

The connection attempt happens as soon as you enter your log in credentials and press the log in (ログイン) button.

Firefox on my computer uses uBlock Origin 1.72.2. uBlock Origin blocks the following domains when visiting the SBI Shinsei Bank log in page:

I can also confirm that the uBlock Origin connection logger blocks at least one connection attempt to a online-metrix.net domain:

This same connection logger does not list the aa.online-metrix.net domain. It seems as though the STUN/TURN port connection attempt evades uBlock Origin.

The online-metrix.net domain somehow belongs to a company called LexisNexis.⁵⁶

I notice similar behavior when I access websites "secured" by CloudFlare. I don't want to completely block STUN/TURN in my firewall as that will keep me, I assume, from doing video calls in my browser.

Using the WebRTC Leak Test I found that allowing connections to random UDP ports reveals my local network IP address. The suits working for my bank are patting each other on their shoulders calling fraud a thing of the past, all thanks to knowing my local network IP address.

In the end, SBI Shinsei Bank is down for unknown reasons anyway: