Error trying to fetch board lists on Firefox

Summary

From Premium Customer (internal: https://gitlab.my.salesforce.com/0016100001FI1Jz):

Wanted to report a bug we’ve seen when using Firefox: When looking at a board with a filter on, like:

GET “/project/-/boards/123?assignee_username=employ1”

And then clicks on an issue on that board, when he clicks the back button, he gets a red alert "An error occurred trying to fetch board lists. Please try again.” It goes away within a second, and the board populates correctly, but in that second the url switches to the usrl without query params, and then again with query params and loads.

Steps to reproduce

Their failed attempts to reproduce this look like this:

looking at the logs, noticed mostly that requests looked like this in the gitlab-ruby production.log:

Started GET “/project/-/boards/123?assignee_username=employ1&" for 172.31.53.17 at 2019-09-04 19:55:56 +0000

While requests that don't show this failure behavior look like this (note above the trailing '&' in the query param):

Started GET “/project/-/boards/123?assignee_username=employ1" for 172.31.53.18 at 2019-09-04 19:55:56 +0000

The ampersand seemed significant, perhaps, and User wasn’t able to reproduce this using Chrome - only Firefox.

What is the current bug behavior?

Issue board with filters provides an error

What is the expected correct behavior?

Issue board with filters loads