Question:
Which employer did Moxie Marlinspike work for in Oct, 2011?

Context:
 Moxie Marlinspike works for Open Whisper Systems from Jan, 2013 to Jan, 2018. 
 Moxie Marlinspike works for Twitter, Inc. from Jan, 2011 to Jan, 2013. 
 Moxie Marlinspike works for Signal Messenger from Jan, 2018 to Dec, 2022. 
 Moxie Marlinspike works for Whisper Systems from Jan, 2010 to Jan, 2011.

Answer:
Twitter, Inc.