Security
Oxford Dictionaries: /sɪˈkjʊərɪti/
(
http://www.oxforddictionaries.com/definition/english/security)
Cambridge Dictionaries: /sɪˈkjʊə.rɪ.ti/
That's what I see when I look up the main sites. The same IPA.
The Oxford Learner's Dictionaries site is somewhat dubious. You should write to the Chief Editor and ask him to explain the discrepancy.