Search Input on Mozilla Firefox overlaps side nav

[cspray]

In Firefox the search input breaks out of the top menu and overlaps the side navigation. This prevents access from the side nav's top most link and suggest edit action within the package documentation.

Here is a screenshot with the broken element.

Here is a screenshot with the element working as intended in Chromium (https://www.chromium.org/).

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OS: Ubuntu 18.10
Mozilla Firefox: 68.0
Chromium: 75.0.3770.90

[qqqrppp]

I have the same problem