SecurityError: The operation is insecure in Firefox Developer edition

Description

With gatsby develop and Firefox Developer Edition (latest version, 69.07b), firefox throws a security error exception when app.js checks if (serviceWorker in navigator), and hence the app cannot be used:

Steps to reproduce

1. Install firefox developer edition
2. Run gatsby develop on any gatsby project (no offline plugin nor anything sw-related)

Expected result

You see the website and can develop it normally.

Actual result

You get the error above and hence cannot do anything (the error triggers the react overlay error and does not let you interact with the site at all)

Environment

  System:
    OS: Linux 5.0 Ubuntu 19.04 (Disco Dingo)
    CPU: (8) x64 Intel(R) Core(TM) i7-8550U CPU @ 1.80GHz
    Shell: 5.0.3 - /bin/bash
  Binaries:
    Node: 10.16.0 - /tmp/yarn--1564036896798-0.009151794373142508/node
    Yarn: 1.17.3 - /tmp/yarn--1564036896798-0.009151794373142508/yarn
    npm: 6.9.0 - /usr/bin/npm
  Languages:
    Python: 2.7.16 - /usr/bin/python
  Browsers:
    Firefox: 68.0
  npmPackages:
    gatsby: ^2.1.27 => 2.13.32
    gatsby-image: ^2.0.31 => 2.2.6
    gatsby-plugin-create-client-paths: ^2.0.4 => 2.1.3
    gatsby-plugin-env-variables: ^1.0.1 => 1.0.1
    gatsby-plugin-manifest: ^2.0.22 => 2.2.3
    gatsby-plugin-react-helmet: ^3.0.8 => 3.1.2
    gatsby-plugin-react-svg: ^2.1.1 => 2.1.1
    gatsby-plugin-remote-images: ^1.0.1 => 1.0.3
    gatsby-plugin-sass: ^2.0.11 => 2.1.3
    gatsby-plugin-sharp: ^2.0.25 => 2.2.8
    gatsby-plugin-typescript: ^2.1.0 => 2.1.2
    gatsby-source-filesystem: ^2.0.23 => 2.1.5
    gatsby-source-s3-image: ^1.5.8 => 1.6.5
    gatsby-transformer-sharp: ^2.1.15 => 2.2.4

[kilburn]

I worked around the issue by disabling the “Delete cookies and site data when Firefox Developer Edition is closed” option:

[areinmeyer]

Just came across this error as well in Firefox 72.

A different option than unchecking the Delete cookies and site data when Firefox is closed is to leave it checked but then go into Manage Permissions option next to the checkmark and add localhost:8000 to the Allow list. Just adding localhost did not work for me, I had to specifically add the port as well.