Prompt Injection Through Tool Output Is Two Events (Your Screens Read One)
Tool output is untrusted because your own systems produce it. That is the part of the OWASP guidance that never makes it into a deployment. The label goes on web pages and email bodies, where an outsider obviously wrote the text. It never goes on the ticket store, the CRM, or the repo, because those are yours. The attacker does not care whose system it is. He cares which field takes free text: the ticket body, the opportunity note, the PR description.