Custom Jinja2 include tags `mdsection include` and `md clean include` re-parse the content of included Markdown files as template code within a non-sandboxed environment. This allows server-side template injection (SSTI), a vulnerability where an attacker injects malicious template directives that are executed by the server, potentially leading to arbitrary code execution. The `MDSectionInclude` and `MDCleanInclude` tags in `Trestle/core/jinja/tags.py` pass file content to the `Parser(self.environment, ...).parse()` function using a standard `jinja2.Environment` instead of a `SandboxedEnvironment`. Consequently, attacker-controlled OSCAL data—such as control statements, part prose, or component descriptions—containing Jinja2 syntax is executed when the include tag re-parses the file.