What was the DAO hack?

Could you please elaborate on the DAO hack? I'm quite curious about this incident that shook the cryptocurrency world. Could you provide a brief overview of what exactly happened during the hack? What vulnerabilities were exploited, and how did it lead to such significant losses? I'm also interested in understanding the consequences of this hack, both in terms of the financial impact and the changes it may have triggered in the cryptocurrency ecosystem. Thank you for taking the time to answer my questions.