IMDSv1, or Instance Metadata Service version 1, is the original version of Amazon Web Services' (AWS) service that allows EC2 instances to access metadata and credentials via HTTP requests to a special local endpoint. While it enables automation and dynamic configuration, IMDSv1 is vulnerable to certain security risks, such as Server-Side Request Forgery (SSRF) attacks, because it lacks authentication and session controls. This exposure can potentially allow attackers to retrieve sensitive information, like instance credentials, if the application running on the instance is compromised. AWS introduced IMDSv2 to address these vulnerabilities by requiring session-based authentication. It is recommended to use IMDSv2 whenever possible to enhance security.