默认情况下，Firefox似乎不发送带有跨域XHR请求的客户端证书.在XHR实例上设置withCredentials=true可以为我解决此问题.请注意，我也没有在Chrome(只有Firefox)上看到此问题.

Firefox appears to not send the client certificate with a cross-origin XHR request by default. Setting withCredentials=true on the XHR instance resolved the issue for me. Note that I also did not see this problem with Chrome--only Firefox.

有关更多信息，请参见此Mozilla Dev Network博客文章一个>.特别是以下语句:

For more info see this Mozilla Dev Network blog post. In particular, the following statement:

默认情况下，在跨站点XMLHttpRequest调用中，浏览器将 不发送凭据.调用XMLHttpRequest对象时，必须设置一个特定的标志.

By default, in cross-site XMLHttpRequest invocations, browsers will not send credentials. A specific flag has to be set on the XMLHttpRequest object when it is invoked.