What type of web application security threat did Jack identify during his investigation?

The choice indicating software and data integrity failure accurately reflects a critical web application security threat. This type of threat occurs when the data or software within an application is manipulated or compromised, leading to unauthorized changes that can affect the integrity, accuracy, or reliability of the information.

In many scenarios, this can happen through various methods such as tampering with code or exploiting vulnerabilities to alter data. For instance, if an attacker gains access to modify backend databases or configuration files, it can disrupt application functionality or lead to misleading information being presented to users. Consequently, ensuring integrity in software and data is essential for maintaining trust and security in web applications.

Other types of threats, while serious, don't encompass the specific nuances of this integrity failure. Injection attacks involve inserting malicious code into an application, while denial of service focuses on making a service unavailable to users. Phishing typically involves deception to steal sensitive information, which does not directly align with the integrity failure context that Jack identified in his investigation.