In Unsafe.java I see:

     * @exception SecurityException if a security manager exists and its
     * <code>checkPropertiesAccess</code> method doesn't allow
     * access to the system properties.
     */
    @CallerSensitive
    public static Unsafe getUnsafe() {
        Class<?> caller = Reflection.getCallerClass();
        if (!VM.isSystemDomainLoader(caller.getClassLoader()))
            throw new SecurityException("Unsafe");
        return theUnsafe;
    }

but the spec looks wrong because it doesn't check whether there is a security manager, unlike code elsewhere. And what's up with checkPropertiesAccess?