Failure to import references with 'HTTPS only mode' in Firefox

[osthomas]

In Firefox, there is an option to automatically upgrade all HTTP connections to HTTPS (Edit -> Settings -> Privacy and Security -> bottom of the page).

When this setting is enabled, opening a non-HTTPS address results in an error. Trying to import a reference from such a location with the JabRef browser extension fails.

Steps to reproduce:

1. For example, check the following journal website: https://genomebiology.biomedcentral.com/
2. Enable HTTPS Only Mode in Firefox
3. Navigate to any article on the site
4. Try to import it to JabRef. The import will fail. The console will show:

Error: HTTP request to http://citation-needed.services.springer.com/... rejected with status 0 
uncaught exception: HTTP GET http://citation-needed.services.springer.com/... failed with status code 0

5. Disable HTTPS Only Mode and try again. The import will then work.

Importing the same article with the Zotero Connector works, even with HTTPs Only Mode enabled. The same error is shown in the console, but they seem to implement a fallback mechanism, although I don't know what it is.