AutoMapper is a convention-based object-object mapper in .NET. Versions prior to 15.1.1 and 16.1.1 are vulnerable to a Denial of Service (DoS) attack. When mapping deeply nested object graphs, the library uses recursive method calls without enforcing a default maximum depth limit. This allows an attacker to provide a specially crafted object graph that exhausts the thread's stack memory, triggering a "StackOverflowException" and causing the entire application process to terminate. Versions 15.1.1 and 16.1.1 fix the issue.