In this study, we examine how the performance of companies using cryptocurrencies is affected by the major external events about cryptocurrencies. The subject of our study is the reactions of the stock market on the firm's disclosure of events related to digital currencies. We identified firms that included the four major cryptocurrencies (Bitcoin, Ripple, Litecoin, and Ethereum) in their financial reports from the Edgar database. We identified major events related to cryptocurrencies and

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... ted an event study analysis to determine the effects of the events on stock market prices of the companies. Preliminary results indicate a significant effect of external events on firm performance. The extent of effects from regulatory and government-related events and external security breach events as well as industry-related events helps us understand the significance of the investors' attention to any disclosures of cryptocurrency-related events.