Review Go for command and template injection
exec with sh -c, and text/template used where html/template is required, are the two classic Go review findings.
Tag: ssti
Spot template injection in Python web code
render_template_string or f-string templates built from user input give Jinja SSTI and full RCE.
Confirm SSTI fast, then jump straight to RCE
A polyglot probe tells you the engine in one shot; from Jinja2 or Freemarker the path to command execution is short.