cannot save change for project jira integration with firefox in 13.7.4

Summary

Since updating gitlab from 13.6.3 to 13.7.4 saving changes for the jira integration of projects is not working anymore when using firefox. The button turns into the spinning variant and never changes in firefox 84 on ubuntu 20.04.

Editing jira integations on group level still works.

Steps to reproduce

Go to -/settings/integrations/jira/edit of a project and click save changes.

We see this on two separately managed self hosted instances.

The problem does not appear with chromium.

Clearing the firefox browser cache does not help.

Relevant logs and/or screenshots

It appears no request to gitlab is made (nothing seen in firefox network connection console) and no logs appear on the server

Results of GitLab environment info

Expand for output related to GitLab environment info

omnibus installation

System information
System:		Debian 10
Proxy:		no
Current User:	git
Using RVM:	no
Ruby Version:	2.7.2p137
Gem Version:	3.1.4
Bundler Version:2.1.4
Rake Version:	13.0.1
Redis Version:	5.0.9
Git Version:	2.29.0
Sidekiq Version:5.2.9
Go Version:	unknown
GitLab information
Version:	13.7.4-ee
Revision:	368b4fb2eee
Directory:	/opt/gitlab/embedded/service/gitlab-rails
DB Adapter:	PostgreSQL
DB Version:	11.9
URL:		xxx
HTTP Clone URL:	xxx
SSH Clone URL:	xxx
Elasticsearch:	no
Geo:		no
Using LDAP:	yes
Using Omniauth:	yes
Omniauth Providers:
GitLab Shell
Version:	13.14.0
Repository storage paths:

• default: /var/opt/gitlab/git-data/repositories GitLab Shell path: /opt/gitlab/embedded/service/gitlab-shell Git: /opt/gitlab/embedded/bin/git