[Affected versions]:
Nightly 68.0a1

[Affected platforms]:
Platforms: all

Steps :

1. Launch the Firefox Browser and reach https://www.icloud.com/#numbers
2. Login and create a blank excel file.
3. Click one of the cell and then try to navigate using the arrow keys.

Expected Results :

The user should be able to navigate the table cells using the arrow keys.

Actual Results :

The user is unable to navigate any of the cells using the arrow keys.

Please note that this issue is already logged in Github as well: https://github.com/webcompat/web-bugs/issues/28031

Here are the results from the mozregression:

changeset: c19f2cea4987db5855c65b7128f10643a4eef99b
pushlog_url: https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=1e6febc9f5af217779860536398cd1c60122e2e1&tochange=c19f2cea4987db5855c65b7128f10643a4eef99b

I can reproduce this issue in Firefox 65 & 66 for MacOS.

Setting dom.keyboardevent.keypress.hack.dispatch_non_printable_keys to *.icloud.com seems to get us around this. Haven't tested for other breakage with this pref set.

Masayuki - maybe you could look into this issue for us please?

Setting dom.keyboardevent.keypress.hack.dispatch_non_printable_keys to *.icloud.com seems to get us around this.

That makes this a regression of bug 1440189, then, which we shipped to release in bug 1496288.

(In reply to Adam Stevenson [:adamopenweb] from comment #1)

Setting dom.keyboardevent.keypress.hack.dispatch_non_printable_keys to *.icloud.com seems to get us around this. Haven't tested for other breakage with this pref set.

Masayuki - maybe you could look into this issue for us please?

Well, sounds like that we should do similar to bug 1536453. If *icloud.com does not aware of our new behavior, I think that all of them are designed for our legacy behavior. So, I think that adding it to the blacklist makes sense. On the other hand, if icloud has a preview of html files (like README.md of github), such files work differently in *.icloud.com from the other places. (Sorry, I'll take another PTO on the next Monday.)

We got an update from Apple and they think they have a patch. Rares, could you please try to verify?

Hi, I retested this issue and it no longer occurs on any version of Firefox Beta, Release or the latest Nightly, I will mark it as WorksForMe.