Problem with content blocked error/ warning when trying to run a web plugins example

  • 8 April 2020
  • 5 replies

Dear Miro dev Community,


I’m trying to run the ‘Stickers and Shapes’ web plugin example code in my Sandbox running a ngrok server locally. Although the SDK loads and the plugin in being initialised, I’m getting the following error/ warning: [blocked] The page at about:blank was not allowed to display insecure content from<file path> (see screen grab below). I’m using Safari on a Mac.


I’d really appreciate if you could provide some advice. 


Many thanks!



Best answer by Boris Borodyansky 10 April 2020, 07:44

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5 replies

Userlevel 4
Badge +1

Hey Melanie!

The first thing I would do is try https link for the ngrok, that’s possibly the issue.


Using Chrome In Windows.

I get the same problem when publishing code on github:


Same problem replicated with Edge: Refused to frame '' because an ancestor violates the following Content Security Policy directive: "frame-ancestors 'none'".


Using Firefox I get “Loading plugin | JIRAPasteSync | 3074457353344029668 |” - seems OK, but later a timeout “Plugin initialization timeout | JIRAPasteSync | 3074457353344029668”


I get the same problem when setting to webplugin adress to miro example:

If I understand it correctly, to get this to work there are a few different options? Miro needs to:

  • Provide a “whitelisting” option for each webplugin source location?
  • Provide a “” proxy adress option for webplugin source location?
  • Enable miro to run as a self hosted service on any source location

Probably a bunch of other ways to solve this?

Userlevel 4

Hello Per,


It looks like the web-plugin url that you have provided to Miro is the url of your index.html file. This won’t work because is a Github page and Miro needs just a url that serves the raw index.html file.

You can use Github Pages to serve the code from your Github repo:


Then, the web-plugin url that you provide to Miro will be from It will look like:

and it should work just fine.


Otherwise, you can also try hosting your web-plugin code in another service, like Netlify, Vercel or Heroku, to name a few.


I hope this helps.


Kind regards.



Thanks for the help - this solved my problem!:grinning: