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Last week , we reported about a cryptographer who found a supposed vulnerability in WhatsApp and later gave an interview to The Guardian explaining the matter .
 ( discover vulnerability: found,  a supposed vulnerability: vulnerability, WhatsApp: vulnerable system, a cryptographer: discoverer, Last week: time) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: phishing, data breach, ransom, discover vulnerability, patch vulnerability, Arguments type: vulnerable system, capabilities, vulnerability, number of victim, issues addressed, compromised data, damage amount, common vulnerabilities and exposures, victim, patch number, number of data, tool, discoverer, time, purpose, place, payment method, releaser, vulnerable system version, attacker, supported platform, patch, price, vulnerable system owner, trusted entity, attack pattern. 
Text: {0} 
Answer:
 ( discover vulnerability: found,  a supposed vulnerability: vulnerability, WhatsApp: vulnerable system, a cryptographer: discoverer, Last week: time) 