Scanning using a mouse button ex: Mouse 4 does not work on firefox

[KSores]

Description
Set Scanning input to Mouse 4 (forward button on the mouse)
try scanning text with Mouse 4.

this works fine on chromium based browsers but does not work on firefox.

Browser version
Firefox 145.0 (64-bit)

Yomitan version
Yomitan Popup Dictionary 25.10.28.0

Exported settings file

yomitan-settings-2025-11-10-23-58-27.json