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The alleged weakness in WhatsApp ’s encryption system was documented by Tobias Boelter , a cryptography and security researcher at the University of California , and branded a " backdoor " today in The Grauniad .
 discover vulnerability: was documented
Please tell me event type and its trigger word from given type options. Output format is "type: trigger".  Option: phishing, data breach, ransom, discover vulnerability, patch vulnerability 
Text: {0} 
Answer:
 discover vulnerability: was documented