Edit pull request modal overflows in Safari 14.0.3

Issue Summary

Safari 14.0.3, released in February 2021, introduced a bug with overflow containers styled with vertical-direction flex boxes.

In Bitbucket Server, this impacts the Pull Request Edit Modal, which overflows when the pull request description is long. View attached screenshot

Steps to Reproduce

1. Create pull request with long description
2. Open the edit pull request modal in Safari 14.0.3

Expected Results

Content stays inside the modal.

Actual Results

Content overflows the bounds of the modal.

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available