Affected versions

• 68.0a1 (2019-03-24)
• 67.0b4
• 66.0.1

Affected platforms

• Windows 10x64
• macOS 10.14
• Ubuntu 16.04

Steps to reproduce

1. Launch FF.
2. Go to Office365 login page.
3. Login with valid credentials.
4. Select a new blank word document.
5. Input any random string in the document.
6. Cut/copy that string from the document.
7. Paste it and then select it whole(double click or ctrl+a)
8. Input any text while string is selected.

Expected result

• The selected string gets replaced if it is selected when inputting new text in the document.

Actual result

• The new inputted text doesn't replace the string but instead adds the new text to the existing one(happens with a flicker).

Regression range

• N/A since the fix for this issue is already known.

Additional notes

• Issue was submitted as per discussed in Slack group #thepowerrrrpoint and we have concluded that this issue is solved if changing the value of dom.keyboardevent.keypress.hack.use_legacy_keycode_and_charcode pref to *.officeapps.live.com

This is fixed via bug 1538966.