while inputting some words into a website with Firefox I’ve got an HTTP 403 error. In the mean time the browser has got „strict-origin-when-cross-origin“ as referer:

Send the origin, path, and querystring when performing a same-origin request. For cross-origin requests send the origin (only) when the protocol security level stays same (HTTPS→HTTPS). Don't send the Referer header to less secure destinations (HTTPS→HTTP).

Do the 403 error and the “strict-origin-when-cross-origin” referrer have a relationship? In what case “strict-origin-when-cross-origin” can happen?