Autocomplete goes haywire when using backspace on Firefox mobile

[catzkorn]

• Sourcegraph version: Sourcegraph.com on 3rd september 2020
• Platform information: Sourcegraph cloud (https://sourcegraph.com/search) on Mobile (pixel 2XL) using Firefox version 80.1.2(build #2015761283).

Steps to reproduce:

Please see video : https://streamable.com/1h63jb

You can see which keys are being pressed on the keyboard.

1. Using Firefox 80.1.2(build #2015761283) on mobile, open https://sourcegraph.com/search
2. Type 'lang' into search and press space, a second lang will be filled in
3. Press backspace to delete the duplicate lang, search field has 'lan' repeated in it many times.

Expected behavior:

When inputting a word in full (e.g lang) and pressing space, it should not autofill another instance of lang. When pressing backspace, it should remove previous text.

Actual behavior:

After inputting a word and pressing space, a second instance of that word comes up. When pressing backspace to remove the duplicate word multiple instances of the word 'lan' is created.

Note

I have tested on Chrome mobile, and it is working as intended.