Affected versions

• Firefox 74.0b8
• Latest Nightly 75.0a1
• Firefox 73.0.1

Affected platforms

• Ubuntu 18.04 64bit
• macOS 10.13
• Windows 8.1 64bit
• Windows 7 32bit

Steps to reproduce

1. Open Firefox with a new profile
2. Make sure the following preferences are correctly set:
   extensions.formautofill.available -> on
   extensions.formautofill.creditCards.available -> true
3. Make sure you have at least 1 address saved in the Autofill addresses section. (about:preferences#privacy / Forms and Autofill / Saved Addresses)
4. Save a credit card entry in about:preferences#privacy / Forms and Autofill / Saved Credit Cards.
5. Visit the following demopage: https://luke-chang.github.io/autofill-demo/basic_cc.html
6. Double click on Name field.

Expected result

• Autofill dropdown is properly displayed.

Actual result

• There is a scrollbar in the right of the dropdown area.

Regression range

• Not a recent regression, will investigate if this is a regression or not ASAP.

Additional notes

• This is only reproducible in normal window the first time the autofill is used but, can be reproduced every time autofill is displayed in a different private window.

Running mozregression, I found out that is indeed a regression from 2019-02-07. I see bunch of bugs that entered that nightly build here is the pushlog https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=0def5ac36b5bf1f7f70bd84d3398dfb64d853ba8&tochange=4e98200ee53017fe8cd037abf948ebaabd33f229
I could not go deeper than this unfortunately, builds aren't available on treeherder.

The priority flag is not set for this bug.
:MattN, could you have a look please?

For more information, please visit auto_nag documentation.

Pretty sure this bug has existed for years… it's because the stylesheet only gets appended upon the first opening but it's too late.