Final answer:
The standard for validating off-the-shelf payment applications used in authorization and settlement is the Payment Application Data Security Standard (PA-DSS).
Step-by-step explanation:
The standard for validating off-the-shelf payment applications used in authorization and settlement is the Payment Application Data Security Standard (PA-DSS). This standard is issued by the Payment Card Industry Security Standards Council (PCI SSC) and helps to ensure the secure handling of sensitive cardholder data.
PA-DSS requires that payment applications meet specific security requirements to be validated. These requirements include securing the software, protecting sensitive data, and ensuring compliance with other PCI DSS requirements.