The callback you're redirecting the user to at the end of that flow is forgeable if an attacker knows an azure tenant ID of a different customer, and putting a "Never use the tenant ID value of the tenant parameter to authenticate or authorize users" warning in the docs is only helpful as long as a way to authenticate users exists.
Azure's Weakest Link – Five Full Cross-Tenant Compromises (binarysecurity.no)
310 pointsby swq115a day ago58 comments
unddoch 18 hours ago
If anyone from Microsoft security reads this, could you please do something about login.microsoftonline.com/XXX/v2.0/adminconsent?
birdsongs 16 hours ago
They'll see it, tell a manager, it'll get added as a ticket to an Azure Devops board under the initiative for this month under the epic for employee suggestions, which will be reviewed & prioritised by Copilot and sent to a different middle manager as a weekly summary email and then automatically closed when no human ever interacts with the ticket after three months.
rsalus 16 hours ago
speaking as a FTE at Microsoft... yup
0xWTF 16 hours ago
Glad to know the frozen middle exists among the hyperscalers. High confidence you can swap the entire leadership team and nothing will change.
jiggawatts 12 hours ago
> frozen middle
That’s the best new term I’ve learned in months!
pphysch 9 hours ago
See also "defensive bureaucracy"
Henchman21 16 hours ago
I spent 6 months working as a contractor in MS’ Chicagoland data centers. Nothing worked — phones on the walls ran Windows and did not give dial tone. Security systems unable to function because of Windows updates. Personnel more concerned with their required LinkedIn updates than their jobs. Not one FTE liked their role — everyone had a foot out the door.
When they offered to make me FTE I declined and moved on. Because it was an obvious absolute shit-show.
Sorry for those that are currently employed by MS.
throwup238 9 hours ago
It’s not all bad. When I was there, the Washington campus had a restaurant with a three course menu for $15, designed by a Seattle celebrity chef.
gscott 7 hours ago
Come for the paycheck... stay for the food!
nikanj 12 hours ago
I love that this is the most reliable way to actually contact an actual human working at Microsoft
collabs 6 hours ago
Reaching an actual human at Microsoft isn't enough. You have to reach the correct humans which is a much harder task. For example, you might have an idea. What if azure devops had a field for date component only, not date time, just the date because it would help you in an internal project. Can you find out who to reach? Even if you work at Microsoft, I would bet you cannot. Even when you find a defect in an internal product you are using, getting to a human requires you to go through layers of nonsense. I distinctly remember my manager telling me to not even bother explaining myself to the first support chat and to simply ask them to escalate. I was impressed at how they managed to make security a part of your review though. I never thought getting buy-in to update Newtonsoft.Json would be as easy as it was but a CVE meant you had to update it to whatever made the security flags happy.
Once I could reach the actual engineering team to look at the internal tool to look at the bug I had to report though, they were very responsive. The tool for communicating was cumbersome and made me feel like a vendor / customer relationship even though you are supposed to be the same team but once they realized it was an actual defect and not some harebrained feature request, they fixed it relatively quickly.
wibartle 10 hours ago
That's me. But I don't understand your comment. Could you expand on it, either in a reply or preferably by email or via an MSRC case? You can reply with the vuln number so I can fast route it.
> The callback you're redirecting the user to at the end of that flow is forgeable
The redirect_uri is checked against the app registration. There's a general OAuth problem called "open registration redirects" that applies here, about which we've [blogged](https://www.microsoft.com/en-us/security/blog/2026/03/02/oau...) - but frankly, none of the industry solves this well.
In general, "I can create a link that goes to malware via X endpoint" isn't very interesting - you can also just create a direct link to the malware. Web browsers won't reliably show you the real destination of a link anyhow and even if they did, it's mostly just us hackers who understand URLs at all.
> as long as a way to authenticate users exists.
I'm lost. Entra supports [OpenID Connect](https://learn.microsoft.com/en-us/entra/identity-platform/v2...) for authentication. Most portals that surface admin consent authenticate the user with an OpenID Connect request either immediately before or after the admin consent request.
publlus_enigma 10 hours ago
I'm sure one of the 60,000 employees who have been told they're welcome not to work there anymore, because the line must go up infinitely, will be chomping at the bit to do so.
meekins 20 hours ago
When it comes to the amount of cross-tenant leaks Azure looks to be way ahead the competition. Makes me wonder why enterprises still flock there.
xmcp123 20 hours ago
Same reason as it was in 2002. “No one ever got fired for buying Microsoft.”
Betelbuddy 19 hours ago
Lets get our Cloud...from the same guys who have been unable to provide a freeze screen feature in Teams for 10 years..should be a firing offense...
totallykvothe 19 hours ago
Wdym? Teams freezes my screen all the time!
Betelbuddy 18 hours ago
Yeah that is a feature
I am talking about the most basic capability of a professional presentation tool like exists in Webex, or GotoMeeting or Zoom. And requested...
https://learn.microsoft.com/en-us/answers/questions/4410610/...
by more than 2000 requests across different microsoft discussion boards, including 1044 on one request alone....
siva7 3 hours ago
wow i've been forced to use teams for over a decade.. i didn't even realise such useful features exist in other presentation tools. like there is a world with software that actually makes my life easier!?
adamm255 12 hours ago
When I have to present in Teams I realise how much I lean on that feature in Zoom. Absolutely astonishing that it’s not a feature.
sandeepkd 17 hours ago
It pretty much applies to everything, going along the tide is always easier
ok123456 15 hours ago
In 2026, it's also: "They have FedRAMP, and some "cyber" person told me we need GCC-High to pass an audit."
jon128 14 hours ago
Federal Cyber Experts Thought Microsoft’s Cloud Was “a Pile of Shit.” They Approved It Anyway.
https://www.propublica.org/article/microsoft-cloud-fedramp-cybersecurity-governmentwinrid 15 hours ago
Good time to start.
traceroute66 20 hours ago
> Makes me wonder why enterprises still flock there
Well, when you're already paying Microsoft $/user/month for Intune, Teams&co. you might as well use Azure too.
Only one vendor relationship to manage, and I suspect you probably have to spend far less money than you do with AWS to get some personal attention.
jeffrallen 18 hours ago
Must be convenient to get all your security bugs from one vendor...
waz0wski 18 hours ago
> one vendor relationship to manage
Anyone that's had to deal with Microsoft will tell you this means nothing
If you can even get attention from someone, you'll be bounced between teams and people who barely know the products they are "supporting"
Don't get me started on the Azure and O365 management portals
The only worse support experience I've had was with Oracle where it could take days just to get the boilerplate "send us your logs" response on a Sev1 issue, despite the logs already being provided in the initial ticket
In both cases, this is while at F100 companies with millions of dollars of licensed software and premium support contracts
traceroute66 17 hours ago
> Anyone that's had to deal with Microsoft will tell you this means nothing...
In relation to everything you said in your post, let's just say "trust me, I know".
But you missed the point I was making.
The GP said "Makes me wonder why enterprises still flock there".
And anyone who's had to deal with enterprise procurement knows if you've got a vendor on the list then its easier to deal with that one than push for multiple.
And then there's the whole budgeting thing. If management can see you're already buying every single employee in the org a Teams license, then getting extra budget for some Azure toys will probably be an easier sell then "yeah, I know we're paying Microsoft a lot of money, but can we have some AWS too". Since in their eyes Azure and Teams licenses is the same thing, "money for Microsoft".
Sadly the tech desk experience in enterprises tends to fall low down the list, if it is considered at all.
Sure, in theory, if you've got a good CTO to fight your corner then YMMV, but not everyone does.
rsalus 16 hours ago
I'm convinced all engineers in the O365 org are call center techs in disguise
esikich 16 hours ago
What do you mean "even get attention from someone"? Enterprise contracts have support included. You can get an engineer on the phone within 24 hours. As long as you are competent enough to answer their questions, their support has been fairly good in my experience.
jiggawatts 12 hours ago
The initial support tech is typically outsourced and responds with: “Yes, it is broken… by design.”
Attention means an engineer who can fix the problem, not an off shore phone jockey paid to make you quietly go away.
esikich 6 hours ago
Yes, it's triage. They do the basic steps, get relevant info, and try to figure out the right team to send it to. This is how support everywhere works.
marcosdumay 15 hours ago
Managing a vendor relationship is the act of distributing license usage through your people, reviewing contracts, having somebody that knows when and where you have to send money so that the software keeps working, and making sure you are not doing something against the contract.
With Microsoft that takes several people working full time. Corporations tend to not want more of those relationships to manage.
DANmode 8 hours ago
> Anyone that's had to deal with Microsoft will tell you this means nothing
If anything, having only one vendor to choose from is a disadvantage.
quinnjh 8 hours ago
The management portals are something special. Hunting through 365, exchange, and azure to find policies that apply elsewhere.
magicalhippo 19 hours ago
For us a big part is that they have data centers in our country. It makes for improved latency and also makes a lot of our customers sleep better (justifiably so or not).
Amazon doesn't and regardless nobody feels comfortable using Google, who knows when they'll discontinue a product we would rely on.
So not a lot left to choose from.
toomuchtodo 19 hours ago
Their sales folks are very good with C level folks, from the meetings I've sat in on. They will give you substantial credits and hands on support to build for you, depending on vertical and predicted future spend, especially if you're already at another cloud provider they're trying to pull you from.
Betelbuddy 18 hours ago
AI Agents are salivating at that level of incompetence....
toomuchtodo 18 hours ago
If there is no cost for poor decisions, nothing will be learned. Incentives drive outcomes.
jon128 18 hours ago
Feels. AKA stupidity, ultimately.
giancarlostoro 14 hours ago
I do .NET full time, every shop I've worked at was on Azure. It makes the most sense for .NET developers, but I'd personally prefer to just rent dedicated servers at this point.
publlus_enigma 9 hours ago
Well they're clearly market leaders being that far ahead of the competition. Maybe that's why.
/s
albert_e 20 hours ago
maybe we should tag submissions with dates now?
[2026-10-02]
beginning of curent month feels like two years ago when multiple vulns drop daily
dofm 18 hours ago
[06:00]
"… then put your little hand in mine…"
giovanni_or2 18 hours ago
This guy must be the nightmare of Azure developers, kudos for the incredible work on finding these vulnerabilities!
josteink 12 hours ago
We contract this company at work. They’re clearly capable.
Can confirm that we’re getting our money's worth. :D
giancarlostoro 2 hours ago
Meanwhile they want to fire even more people there.
thewisenerd 21 hours ago
path traversal and IDOR..
likely been active since the inception of these capabilities
wonder if the recommendation to "add randomness to resource names" is because of this (unrelated security by obscurity lol)
chinathrow 20 hours ago
Gotta put these backdoors somewhere.
outworlder 18 hours ago
Ok so.
Microsoft had an egregious cross-tenant vulnerability (really, how many cross-tenant vulnerabilities did other clouds have?).
Vulnerability was reported.
They fixed it - incorrectly. Reported again.
They fixed it this time... and broke the previous fix. So it's vulnerable again.
What a clown show.
waz0wski 17 hours ago
Really not surprising given the history of sloppy coding, elementary authentication mistakes, outsourced "support", and anecdotal reports of horrid internal culture over the past few years
[2026] Erosion of Trust @ Azure
https://news.ycombinator.com/item?id=47616242
https://isolveproblems.substack.com/p/how-microsoft-vaporize...
[2026] https://www.microsoft.com/en-us/security/blog/2026/05/18/sto...
[2025] https://www.cisa.gov/news-events/alerts/2025/07/20/microsoft...
[2025] https://www.securityweek.com/all-microsoft-entra-tenants-wer...
[2024] https://www.cloaked.com/post/microsoft-data-breach
[2023] https://www.reuters.com/world/us/chinese-hackers-stole-60000...
[2023] https://www.wiz.io/blog/storm-0558-compromised-microsoft-key...
[2022] https://www.spiceworks.com/it-security/cloud-security/news/m...
[2022] https://techcrunch.com/2022/03/23/microsoft-lapsus-hack-sour...
[2021] https://www.cpomagazine.com/cyber-security/microsoft-power-a...
[2021] https://www.darkreading.com/cloud-security/microsoft-azure-c...
And this is just the Azure / O365 stuff - there's been thousands of Windows client/server and Office software exploits across the same time period
tencentshill 16 hours ago
They keep forgetting to put "make no mistakes" in the copilot prompt!
xmcp123 20 hours ago
God. I would hate to be the engineer forced to have enough Azure experience to be able to find these bugs and understand Azure’s infrastructure on this level.
Should have been addressed in the Geneva conventions.
anonymous908213 12 hours ago
The outsourcing of coding to LLMs is, in this case, a humanitarian measure.
mapotofu 17 hours ago
“Go to the cloud!”, they said.
The cloud:
Let’s see how their platform design holds up in the coming years, and if it can hold up to LLMs doing more of this same type of discovery and whether MSFT can fix it.
eugenekay 20 hours ago
Reporting cross-Tenant issues as an outsider with a vulnerability chain gets you $$$.
Reporting “theoretical” issues with validation as an Employee gets you a lot of questions as to why you were looking.
Oh well.
traceroute66 20 hours ago
> Reporting “theoretical” issues with validation as an Employee
Microsoft still has employees ? ;)
(Sorry. Low bar. But in all honesty I thought they outsourced the majority of ops. I was surprised to hear in recent news that they actually had that many employees left)
outworlder 18 hours ago
So MSFT discourages employees from reporting vulnerabilities?
That explains a lot.