The crossorigin
attribute on the video
needs to be anonymous
or use-credentials
<video controls autoplay crossorigin="use-credentials">
<source src="http://ronallo.com/demos/webvtt-cue-settings/soybean-talk-clip.mp4" type="video/mp4">
<track label="Captions" kind="captions" srclang="en" src="http://ronallo.com/demos/webvtt-cue-settings/soybean-talk-clip.vtt" id="caption-change-track" default="">
</video>
Mozilla's explanation
crossorigin
This enumerated attribute indicates whether to use CORS to fetch the related image. CORS-enabled resourcescan be reused in the element without being tainted. The allowed values are:
anonymous
Sends a cross-origin request without a credential. In other words, it sends the Origin: HTTP header without a cookie, X.509 certificate, or performing HTTP Basic authentication. If the server does not give credentials to the origin site (by not setting the Access-Control-Allow-Origin: HTTP header), the image will be tainted, and its usage restricted.
use-credentials
Sends a cross-origin request with a credential. In other words, it sends the Origin: HTTP header with a cookie, a certificate, or performing HTTP Basic authentication. If the server does not give credentials to the origin site (through Access-Control-Allow-Credentials: HTTP header), the image will be tainted and its usage restricted.
When not present, the resource is fetched without a CORS request (i.e. without sending the Origin: HTTP header), preventing its non-tainted used in elements. If invalid, it is handled as if the enumerated keyword anonymous was used. See CORS settings attributes for additional information.