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However , the issue was renewed last week when researchers from Ruhr - University Bochum in Germany published a paper on different attacks against network printers and an assessment of 20 printer models .
 ( discover vulnerability: published a paper,  researchers: discoverer, printer models: vulnerable system, last week: time, network printers: vulnerable system, Ruhr - University Bochum: discoverer) 
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: published a paper,  researchers: discoverer, printer models: vulnerable system, last week: time, network printers: vulnerable system, Ruhr - University Bochum: discoverer) 