Trying to copy a cookie from second.com to first.com, with full control of both domains.
Previously an iFrame was used, however this is not able to work across all browsers as it touched on 'third-party cookies' which are hard to implement and impossible in Safari and Chrome.
The new approach uses a SCRIPT tag pointing to second.com and included in the HEAD of first.com. The server-side script is actually a piece of Java which reads the cookies sent with the request (the cookies from second.com) and the JavaScript returned executes on first.com and essentially duplicates the cookie here. This is working great in all browsers except IE, where IE appears to not be sending the second.com cookies with SCRIPT request, so the Java is not able to pickup the cookie value from second.com.
This is surely to do with IE security settings as when I put privacy to the lowest level it is working, but my question is why are the cookies being blocked at all? I thought the SCRIPT tag was not subject to the same origin policy (that AJAX and other technologies have to comply with).
Any solution to this without heading down the P3P privacy policy route?
It's definitely IE security settings, if you're attempting this you'll need to set a P3P compact privacy policy on the page which sets the cookie on first.com, even before you've reached second.com
来源：https://stackoverflow.com/questions/2666376/copying-cookies-cross-domain-why-is-ie-blocking-cookies-other-browsers-are-send