Grafana v8.3.x: "NetworkError when attempting to fetch resource."

[anirudh-ramesh]

• Environment
  • Grafana OSS v8.3.0 and v8.3.6
  • Button Panel v7.0.23
  • OS: Ubuntu 20.04
• Observed behaviour
  • With any URL, any type of request GET/POST
  • With/without a reverse proxy
  • Error message viewable upon clicking the button: NetworkError when attempting to fetch resource.
• How to reproduce:
  • Install Grafana OSS and Button Panel of the versions mentioned
  • Create a new dashboard
  • Create a new panel of the button plugin
  • Replace the URL with any valid URL e.g. Requestbin with GET/POST
  • Click on the button
  • View the error message in the hover text
  • View the Grafana log