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In recent months , several hacking groups have been attacking thousands of publicly exposed MongoDB databases .
 ( data breach: have been attacking,  exposed MongoDB databases: compromised data, thousands: number of data, hacking groups: attacker, recent months: 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:
 ( data breach: have been attacking,  exposed MongoDB databases: compromised data, thousands: number of data, hacking groups: attacker, recent months: time) 