The lead
Researcher demonstrates a self-spreading Word document attack that makes Copilot rewrite financial figures
Maloy has been reporting this to Microsoft since March 2026. Two mitigations later, including Edit with Copilot and a move to GPT-5.5, a reworded payload still worked, and he says no robust fix exists for the vulnerability class.
Hidden white-on-white instructions inside a Word file make Copilot silently change numerical values in financial reports, then copy the same hidden payload into the document it generates. That new internal document becomes the next infection vector, so the attack spreads through normal sharing without the original file.
KRALYSBefore any Copilot or Claude assist on a Kralys deck or model, paste the source text into a plain editor first so hidden instructions cannot ride along, and set the rule now that no AI tool edits a numbers document in place.