Unexpected security footguns in Go's parsers

File parsers in Go contain unexpected behaviors that can lead to serious security vulnerabilities. This post examines how JSON, XML, and YAML parsers in Go handle edge cases in ways that have repeatedly resulted in high-impact security issues in production systems. We explore three real-world attack scenarios: marshaling/unmarshaling unexpected data, exploiting parser differentials, and leveraging data format confusion. Through examples, we demonstrate how attackers can bypass authentication, circumvent authorization controls, and exfiltrate sensitive data by exploiting these parser behaviors.