Which statement defines a zero-day exploit?

A zero-day exploit refers to a cyberattack that takes advantage of a newly discovered software vulnerability for which no patch or fix has yet been released by the vendor. This means developers have had "zero days" to address the vulnerability, leaving systems exposed. The correct option accurately describes this scenario. The other options describe different types of attacks: saturating a network with malicious traffic describes a Denial of Service (DoS) attack; inserting malicious code into a SQL server describes a SQL injection attack; and inserting oneself into a conversation to capture or alter data describes a Man-in-the-Middle (MitM) attack.