A hidden Word prompt can turn Copilot documents into carriers (enklypesalt.com)
A coordinated disclosure describes prompt injection in Copilot for Word: a document can hide instructions in white-on-white text, influence a generated report, then cause Copilot to copy those instructions into the output. That output becomes the next carrier when someone uses it as source material.
The uncomfortable shift is from a bad attachment to a poisoned internal artifact. The author says Microsoft reproduced the broader class after multiple mitigations; the immediate defensive rule is to treat external files as untrusted context, not just untrusted downloads.
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