2026-02-1812:1627274www.bleepingcomputer.com
Microsoft says a Microsoft 365 Copilot bug has been causing the AI assistant to summarize confidential emails since late January, bypassing data loss prevention (DLP) policies that organizations rely…
"Users' email messages with a confidential label applied are being incorrectly processed by Microsoft 365 Copilot chat," Microsoft said when it confirmed this issue.
"The Microsoft 365 Copilot 'work tab' Chat is summarizing email messages even though these email messages have a sensitivity label applied and a DLP policy is configured."
Microsoft has since confirmed that an unspecified code error is responsible and said it began rolling out a fix in early February. As of Wednesday, the company said it was continuing to monitor the deployment and is reaching out to a subset of affected users to verify that the fix is working.
"A code issue is allowing items in the sent items and draft folders to be picked up by Copilot even though confidential labels are set in place," Microsoft added.
Microsoft has not provided a final timeline for full remediation and has not disclosed how many users or organizations were affected, saying only that the scope of impact may change as the investigation continues.
However, this ongoing incident has been tagged as an advisory, a flag commonly used to describe service issues typically involving limited scope or impact.
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There are two issues I see here (besides the obvious “Why do we even let this happen in the first place?”):
1. What happened to all the data Copilot trained on that was confidential? How is that data separated and deleted from the model’s training? How can we be sure it’s gone?
2. This issue was found; unfortunately without a much better security posture from Microsoft, we have no way of knowing what issues are currently lurking that are as bad as —- if not worse than —- what happened here.
There’s a serious fundamental flaw in the thinking and misguided incentives that led to “sprinkle AI everywhere”, and instead of taking a step back and rethinking that approach, we’re going to get pieced together fixes and still be left with the foundational problem that everyone’s data is just one prompt injection away from being taken; whether it’s labeled as “secure” or not.
By carefulfungi 2026-02-1816:531 reply > "The Microsoft 365 Copilot 'work tab' Chat is summarizing email messages even though these email messages have a sensitivity label applied and a DLP policy is configured."
I'd add (3) - a DLP policy is apparently ineffective at its purpose: monitoring data sharing between machines. (https://learn.microsoft.com/en-us/purview/dlp-learn-about-dl...).
Directly from the DLP feature page:
> DLP, with collection policies, monitors and protects against oversharing to Unmanaged cloud apps by targeting data transmitted on your network and in Microsoft Edge for Business. Create policies that target Inline web traffic (preview) and Network activity (preview) to cover locations like:
> OpenAI ChatGPT—for Edge for Business and Network options > Google Gemini—for Edge for Business and Network options > DeepSeek—for Edge for Business and Network options > Microsoft Copilot—for Edge for Business and Network options > Over 34,000 cloud apps in the Microsoft Defender for Cloud Apps cloud app catalog—Network option only
> a DLP policy is apparently ineffective at its purpose
/Offtopic
Yes, MSFT's DLP/software malfunctioned, but getting users to MANUALLY classify things as confidential is already an uphill battle. These are for the rare subset of people that are aware of and compliant with NDAs/Confidentiality Agreements!
By ImPostingOnHN 2026-02-1818:37 Who can blame them, when in the end, it gets ignored anyways?
By godelski 2026-02-193:23 I'm an AI researcher, here's my beliefs (it'll be clear in a second why I say belief and not claim objective facts)
1) you can't be sure it's gone. It's even questionable if data can be removed (longer discussion needed). These are compression machines, so the very act of training is compressing that information. The question really becomes how well that information is compressed or embedded into the model. On one hand, the models (typically) aren't invertible so the information is less likely to be compressed lodslessly. On the other hand, the models aren't invertible, so reversing them is probabilistic and they are harder to analyze in this sense.
2) as you may gather from 1) there's almost certainly more issues like this. There are many unknown unknowns waiting to be discovered. Personally this is why I'm very upset the field is so product focused and that a large portion regards theory as pointless. Theory does two things for us because it builds a deeper and more nuanced understanding. Theory advancing allows us to develop faster as we can iterate on paper rather than through experimentation. This allows us to better search the solution space and even understand our understanding. This also leads to better safety of models as it is necessary to understand them to understand where they fail and how to prevent those failures. Experimentation alone is incredibly naïve. It is like proving the correctness of your programs through testing (see the issues with TDD). Tests are great but they are bounds, not proofs. They can suggest safety, give you some level of confidence in safety, but they cannot guarantee it. We all know that the deeper understanding of your code the better tests you can write, and this is the same thing here. That theory is reducing your unknown unknowns and even before strong proofs are made we can get wider coverage in our testing.
I think we're so excited right now we're blinding ourselves. If we're cutting off or reducing fundamental research then we are killing the pipeline of development. Theory is the foundation that engineering sits on top of. But what worries me is that there's so many unknown unknowns and everyone is eagerly saying "we're just need 'good enough'" or "what's the minimum viable product". These are useful tools/questions but they have limits and it gets dangerous when putting out the minimum at scale
By samch 2026-02-1819:41 Copilot is not a model, to my knowledge. When you’re asking about the data that it was trained on, you are most likely referring to an OpenAI or, in some circumstances, an Anthropic model. Customer data is not used for training the models that run Copilot.
By doctorpangloss 2026-02-1815:333 reply All the vendors paraphrase user data, then use the paraphrased data for training. This is what their terms of service say.
They have significant experience in this. Microsoft software since the 2014, for the most part, is also paraphrased from other people's code they find laying around online.
> All the vendors paraphrase user data, then use the paraphrased data for training. This is what their terms of service say.
It depends. E.g. OpenAI says: "By default, we do not train on any inputs or outputs from our products for business users, including ChatGPT Team, ChatGPT Enterprise, and the API."[0]
[0] https://openai.com/policies/how-your-data-is-used-to-improve...
Why would they want to train on random garbage proprietary emails?
If their models ever spit out obviously confidential information belonging to their paying customers they'll lose those paying customers to their competitors - and probably face significant legal costs as well.
Your random confidential corporate email really isn't that valuable for training. I'd argue it's more like toxic waste that should be avoided at all costs.
By doctorpangloss 2026-02-1914:311 reply Your opinion seems a little unimaginative. To me, since email is the primary work output of millions of Americans, including all of its leaders, there is a lot of opportunity there.
By doctorpangloss 2026-02-2015:07 I guess that's why Anthropic is worth 380b and you and I are worth nothing haha
By moritzwarhier 2026-02-1818:171 reply > Microsoft software since the 2014, for the most part, is also paraphrased from other people's code they find laying around online.
That was pretty funny and explains a lot.
I wish I could do more :(
Instead I always break things when I paraphrase code without the GeniusParaphrasingTool
This is exactly why I moved to self hosted code in 2017.
While I couldn’t have predicted the future, even classic data mining posed a risk.
It is just reality that if you give a third party access to your data, you should expect them to use it.
It is just too tempting of a value stream and legislation just isn’t there to avoid the EULA trap.
I was targeting a market where fractions of a percentage advantage were important which did drive my what at the time was labeled paranoia
By observationist 2026-02-1816:043 reply Seems like every day there's another compelling reason to switch to Linux. Microsoft is doing truly incredible work this year!
I recently switched my work laptop from a Dell to a MacBook. I found out that windows 11 has so much corporate bloat, than even MS apps like outlook, office and OneDrive functions better on a Mac than on Windows 11.
By allthetime 2026-02-1822:59 It’s been this way forever.
Apple not doing much better, but from the other end.
Microsoft releasing overly ambitious features with disastrous consequences.
Apple releasing features so unambitious it's hard to remember they're there.
By observationist 2026-02-1816:27 Performance is also degrading on iphones as software bloats, and/or they're up to their old shenanigans and making older phones unbearable to force people to buy the newest ones.
Big tech is reaping what they've sown in a very satisfying way.
By import 2026-02-1816:37 We can safely assume that Apple will do much better compared to MS until they put AI to the Finder and Dock.
By varispeed 2026-02-1817:25 Don't forget Apple handwaving serious security issues of their devices - users still cannot even check if their devices are compromised and only thing Apple can do here is "lockdown mode" - which again, after compromise is likely useless anyway.
By marcosdumay 2026-02-1818:421 reply The problem with the Microsoft features is really not excessive ambition.
Half of the time it's open user hostility and blatant incompetence. The other half it's just the incompetence. Ambition doesn't enter the picture at all.
Eh. I think it is ambition. It's a lot product managers coming up with ideas, I think, and teams with a mandate to release those ideas.
By observationist 2026-02-1822:561 reply Yes, and those ideas are user hostile and poorly conceived, badly executed, and incompetently built.
A remote code execution exploit in notepad?! That's not professional, or skillful, or well done. Unnecessary feature bloat and change for the sake of change, because some MBA dork wants to justify their department and continued employment by checking boxes on spreadsheets.
There's no innovation or skillful, well built features. There's hardly any consideration of users at all, except as net continuing depositors of money into Microsoft coffers. Features and updates are nothing more than marketing slop and manipulation of enterprise into renewing subscriptions and purchasing the latest version of new hardware.
edit:
I just don't think that you can point at a company whose entire foundational product, Windows, the operating system that's pretty much default for most of the world, and say that they're not completely and utterly failing as a company when their single most compelling "feature" is that the OS can run Excel.
It's the year of the Linux desktop, fire it up and never look back!
I agree except for Microsoft "failing". Windows is failing. Microsoft has moved onto other things.
By marcosdumay 2026-02-1916:461 reply The two moats Microsoft has are Windows and Office. All of their revenue generating products only sell because of those two.
By marcosdumay 2026-02-2018:44 Yes, that was true a decade ago too.
By blibble 2026-02-194:10 azure is just as bad, if not worse
By otterley 2026-02-194:17 The problem would still exist if you use Linux. This is a cloud service issue, not an OS issue.
By childofhedgehog 2026-02-1813:214 reply > However, this ongoing incident has been tagged as an advisory, a flag commonly used to describe service issues typically involving limited scope or impact.
How is having Copilot breach trust and privacy an “advisory”? Am I missing something?
By dijit 2026-02-1814:58 Advisory doesn't have the same meaning in security research as it does in the english language.
Unfortunately "Advisory" is a report written about a security incident, like an official statement about the bug, it's impact, and how to fix it -- which differs from the english meaning... it's not meant to mean to "advise" people or to "take something" under "advisory" (which, is a very soft statement typically).
https://www.merriam-webster.com/dictionary/advise meaning 2: to give information or notice to : INFORM
An advisory gives notice and/or warns about something, and may give recommendations on possible actions (but doesn’t have to).
By _verandaguy 2026-02-1815:51 Words have multiple meanings depending on context, and here it's at best ambiguous. In the context of security incidents, logging, auditing, etc., "advisory" is often used as a severity level (and one of the lower ones at that).
So, yes, technically, it's de-facto advisory to publish this information, but assigning "advisory" as a severity tag here is questionable.
By bpodgursky 2026-02-1817:01 If you inflate severity, people simply ignore incident warnings.
What's the actual action needed here by a security team? None. You can hate it or not care but the end of the day there's no remediation or imminent harm, just a potential issue with DLP policies. Don't make it look like a 0-day that they actually have to deal with.
By lich_king 2026-02-1815:50 The LLM that wrote this nearly content-free story doesn't know what it's talking about.
The basic distinction in the infosec industry is that advisories are what you publish to tell customers that you had a bug in your product that might have exposed them or their data to attacks and you want them to take some specific action (e.g., upgrade a package, review logs); while an incident report is what you publish when you know that the damage happened, it involved your infrastructure, and you want to share some details about happened and how you're going to prevent it from happening again.
Because the latter invites a lot more public attention and regulatory scrutiny, a company like Microsoft will go out of their way to stick to advisories whenever possible (or just keep incidents under wraps). It might have happened at some points in their history, but off the top of my head, I don't recall Microsoft ever publishing a first-party security incident report.
