What is the usage of the cross-origin attribute in HTML5?

The official specification states cross-origin attribute as −

The crossorigin attribute is a CORS settings attribute.
Its purpose is to allow images from third-party sites that allow
cross-origin access to be used with canvas.

When it is combined with CORS header, it would allow images defined by the <img> element, loaded from foreign origins to be used in canvas. The procedure would be like being loaded from the current origin.

You can use it to solve JavaScript errors like to log js errors −

if (securityOrigin()->canRequest(targetUrl)) {
   msg = myError;
   line = myLineNumber;
   source = sourceURL;
} else {
   msg = "Error!";
   source = String();
   line = 0;
}