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Cybersecurity experts say the hackers behind the " WannaCry " ransomware , who demanded $ 300 payments to decrypt files locked by the malware , used a vulnerability that came from U.S. government documents leaked online .
 ( ransom: demanded,  $ 300: price, the " WannaCry " ransomware: tool, the hackers: attacker) 
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:
 ( ransom: demanded,  $ 300: price, the " WannaCry " ransomware: tool, the hackers: attacker) 