This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
Node.nodePrincipal read-only property returns the
nsIPrincipal object representing current security context of the node.
principalObj = element.nodePrincipal
This property is read-only; attempting to write to it will throw an exception. In addition, this property may only be accessed from privileged code.
Not in any specification.