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Qubes OS , an operating system that uses Xen to isolate applications inside virtual machines , also put out an advisory warning that an attacker who exploits another vulnerability , for example inside a browser , can exploit this Xen issue to compromise the whole Qubes system .
 ( discover vulnerability: put out an advisory warning,  another vulnerability: vulnerability) 
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: put out an advisory warning,  another vulnerability: vulnerability) 