Test Content-Security-Policy violation handling

Hi, I am developing a website of my own and in that website I want to implement a handler for Content-Security-Policy violation reports. I want to test if this handler works as I expect and therefore I have configured a webpage such that is will report CSP violations (I see them in the web developer console) and I want to have them sent to my application's CSP-violation handler. In my test environment, the application is running on localhost. I have run my web application both on HTTP and HTTPS (with a self-signed certificate), but in neither case Firefox is sending any reports to my application. My CSP headers look as follows: Content-Security-Policy: report-uri http://localhost:5281/csp-violation;base-uri 'none';default-src 'self';form-action 'none';frame-ancestors 'none';report-to csp-viol;script-src 'unsafe-eval' 'nonce-9FuQ3NuVoW66DT1ZU4w9EPSymnHE1/hg';style-src 'unsafe-eval' 'nonce-9FuQ3NuVoW66DT1ZU4w9EPSymnHE1/hg' Reporting-Endpoints: csp-viol=http://localhost:5281/csp-violation Report-To: {"group":"csp-viol","max_age":10886400,"endpoints":[{"url":"http://localhost:5281/csp-violation"}]} When I run my application using HTTPS, all HTTP in the endpoints will also be HTTPS. I have verified that when I post something by hand to http://localhost:5281/csp-violation, my handler is executed, so that is not the issue. I believe that Firefox is just not sending the reports. Is there a way to configure Firefox such that it will send the CSP violation reports to my application when run on HTTP(S) on localhost? Sincerely, Marcel