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An exploit in the Android operating system means almost 40 percent of users are vulnerable to screen - hijacking apps , but it is unlikely to be fixed until winter .
 ( discover vulnerability: are vulnerable,  screen - hijacking apps: vulnerability, the Android operating system: vulnerable system) 
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: are vulnerable,  screen - hijacking apps: vulnerability, the Android operating system: vulnerable system) 