1. A system for bug discovery using event reports, comprising: an interface configured to: receive symptom data extracted from event reports from a user system, wherein the symptom data is stored in a symptom database, and wherein the symptom data comprises one or more symptoms each with a corresponding symptom occurrence time; a processor configured to: determine an existence of one or more bugs of the user system based at least in part on a result of querying the symptom database using a bug definition.