Yes, it is.

stack@devstack3:~$ stack_update_last http://dunsmor.com/heat/heat-templates/rackspace/Wordpress_Single_Instance.yaml "Foo=bar;DBUsername=wp;DBPassword=verybadpassword2"           
ERROR: Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/eventlet/wsgi.py", line 384, in handle_one_response 
    result = self.application(self.environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 130, in __call__                
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 195, in call_func               
    return self.func(req, *args, **kwargs)
  File "/opt/stack/heat/heat/common/wsgi.py", line 306, in __call__
    eventlet.patcher.monkey_patch(all=False, socket=True)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1296, in send               
    application, catch_exc_info=False)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1260, in call_application   
    app_iter = application(self.environ, start_response)
  File "/opt/stack/heat/heat/common/auth_password.py", line 74, in __call__
    return self.app(env, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 130, in __call__                
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 195, in call_func               
    return self.func(req, *args, **kwargs)
  File "/opt/stack/heat/heat/common/wsgi.py", line 306, in __call__
    eventlet.patcher.monkey_patch(all=False, socket=True)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1296, in send               
    application, catch_exc_info=False)
  File "/usr/local/lib/python2.7/dist-packages/webob/request.py", line 1260, in call_application   
    app_iter = application(self.environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 144, in __call__                
    return resp(environ, start_response)
  File "/usr/lib/python2.7/dist-packages/routes/middleware.py", line 131, in __call__              
    response = self.app(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 144, in __call__                
    return resp(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 130, in __call__                
    resp = self.call_func(req, *args, **self.kwargs)
  File "/usr/local/lib/python2.7/dist-packages/webob/dec.py", line 195, in call_func               
    return self.func(req, *args, **kwargs)
  File "/opt/stack/heat/heat/common/wsgi.py", line 612, in __call__
    serialized by requested content type.
UnknownUserParameter_Remote: The Parameter (Foo) was not defined in template.
Traceback (most recent call last):
                   
  File "/opt/stack/heat/heat/openstack/common/rpc/amqp.py", line 435, in _process_data             
    **args)        
                   
  File "/opt/stack/heat/heat/openstack/common/rpc/dispatcher.py", line 172, in dispatch            
    result = getattr(proxyobj, method)(ctxt, **kwargs)
                   
  File "/opt/stack/heat/heat/engine/service.py", line 55, in wrapped
    return func(self, ctx, *args, **kwargs)
                   
  File "/opt/stack/heat/heat/engine/service.py", line 291, in update_stack
    env, **common_params)
                   
  File "/opt/stack/heat/heat/engine/parser.py", line 96, in __init__
    user_params=self.env.params)
                   
  File "/opt/stack/heat/heat/engine/parameters.py", line 349, in __init__
    self._validate(user_params)
                   
  File "/opt/stack/heat/heat/engine/parameters.py", line 386, in _validate
    raise exception.UnknownUserParameter(key=param)
                   
UnknownUserParameter: The Parameter (Foo) was not defined in template.