contentscript.js, line 19: TypeError: event is undefined

[RJVB]

When browsing stories on Instagram, each time I move to the next the following line is printed on the calling terminal:

JavaScript error: moz-extension://fb536ad0-4d75-4dc2-a6d7-f71c529653ef/js/contentscript.js, line 19: TypeError: event is undefined

Please complete the following information when submitting a feature request or bug report.

• Extension version: v7.1.5
• Browser name & version: Firefox 132.0
• Operating system & version: Mac OS X 10.9.5

[RJVB]

I can reproduce this error on Linux with Firefox Dev. Edition (133.0) when I toggle browser.dom.window.dump.enabled to true in about:config :

Here the error reporting is a little more useful:

JavaScript error: moz-extension://c0732029-4f75-4bcb-9937-65c7806c3582/js/contentscript.js, line 19: TypeError: can't access property "keyCode", event is undefined
JavaScript error: moz-extension://c0732029-4f75-4bcb-9937-65c7806c3582/js/contentscript.js, line 19: TypeError: can't access property "keyCode", event is undefined

[RJVB]

See https://stackoverflow.com/questions/15555687/event-keycode-not-working-in-firefox (historical) and https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/keyCode (indicating that the keyCode property is deprecated and its modern replacements.