Document-borne AI worms can self-propagate through Copilot for Word

Canopy9560

Author here. This post covers a coordinated disclosure with Microsoft (MSRC) regarding a vulnerability class that allows attacker-controlled instructions in an attached document to hijack Copilot for Word. It manipulates the AI to alter the output text (e.g., halving financial figures) and append the attack prompt into the new document concealed as white text. Because the downstream document now carries the payload, it acts similarly to an AI worm across normal user workflows. Microsoft deployed multiple fixes over a 144-day coordination period, but the broader vulnerability class remains unmitigated and exploitable because it exploits fundamental limitations of current LLMs. When attacker instructions are combined with legitimate information the model's context window, the tokens being inspected participate in the act of inspection, meaning current LLM architectures provide no reliable boundary between intention and interpretation.

anon48293

“ At the time of publication, no robust mitigation for the broader vulnerability class is available.” Well, that sounds promising..

simonw

> Malicious instructions hidden in an externally shared document could make Copilot alter drafted or edited documents in Word and propagate the attack to new documents. Oh no.

skybrian

Why is it possible to have hidden text in a Word document? Why should the AI have access to that text?

teodosin

I may be naive here but can the hidden text not be flagged or outright removed before being passed to copilot? Why would there not be consideration for what a human user can see, especially if the hidden text was added by copilot in the first place?

woadwarrior01

Could this possible be the first AI worm? Or are there any priors to this?

nticompass

It's VBScript/macro worms all over again!

ghlancet

I mean all your data is already exfiltrated to Copilot, so a little extra worm cannot hurt. It is fun to see how all AI narratives are collapsing.

RaSoJo

Oh but for an alternative to Excel Purged I would have All things Microsoft from my (controllable) world

idiotsecant

LLMs should be viewed with the same terror as a reckless toddler who knows some bash syntax. Deeply embedding them into important and privileged systems will be the end of us.

utopiah

3 months from first contact to... nothing. Surely those big corps peddling AI dev can't be taken seriously.

nottorp

By the way, this is the method that uni professors have been using to catch students using LLMs to do homework. Paste any document in any LLM and you'll risk that, it's not something Microsoft specific.

dev_l1x_be

I am wondering when the whole Excel/Word universe is going to die. One can only hope.

averagjoe

I'm a programmer and a web-based AI user, but I don't want AI running on my local machine in any form. I've uninstalled Copilot and disabled AI in all local applications including the browser itself for exactly the reason described in this article. There's no way to protect your data from such an AI confusion attack by design. AI cannot discern your prompts versus text in file. The fact that an AI enabled word processor or email app could follow instructions embedded in a run-of-the-mill document or email is insane. Switching to Linux, BSD or another open source operating system is the only real solution to this problem.

piker

White text still works! There are many approaches today. Check out https://tritium.legal/blog/noroboto where we tricked frontier algorithms into reading different Unicode values from those presented by the fonts in the document.

josefritzishere

It's increasingly clear that AI needs to be heavily regulated to be safe for public use. It needs to grow out of it's "wild west" model.

westurner

Yesterday I was reading model thinking output and learned that the model has concerns about shell backticks in commit messages.

officeplant

Look on the positive side, the faster AI causes more harm the faster our bosses might wake up and push anti-AI company policies! Oh who am I kidding, ya'll asked for this reality. I will take great joy in the suffering from my AI-less soapbox.

rwmj

> "At the time of publication, no robust mitigation for the broader vulnerability class is available" Isn't it obvious by now that it's never going to be possible to fix this kind of thing, at least until we stop mixing up instructions with data.

richardstahl

History does not repeat but it rhymes. Strong Macro Virus vibes incoming!