I work on security at PostHog. We resolved these SSRF findings back in October 2024 when this report was responsibly disclosed to us. I'm currently gathering the relevant PRs so that we can share them here. We're also working on some architectural improvements around egress, namely using smokescreen, to better protect against this class of issue.
piccirello 119 days ago [-]
Here's the PR[0] that resolved the SSRF issue. This fix was shipped within 24 hours of receiving the initial report.
It's worth noting that at the time of this report, this only affected PostHog's single tenant hobby deployment (i.e. our self hosted version). Our Cloud deployment used our Rust service for sending webhooks, which has had SSRF protection since May 2024[1].
Since this report we've evolved our Cloud architecture significantly, and we have similar IP-based filtering throughout our backend services.
What I don't quite understand: Why is the Clickhouse bug not given more scrutiny?
Like that escape bug was what made the RCE possible and certainly a core DB company like ClickHouse should be held accountable for such an oversight?
matmuls 119 days ago [-]
ssrf was the entry point, and clickhouse is supposed to be an internal only service, but one could reach it only with that ssrf, so hence less of "scrutiny". The 0day by itself wouldnt be useful, unless an attacker can reach clickhouse, which they usually can't.
thenaturalist 119 days ago [-]
But if they do, prohibiting SQL injection, a critical last mile vulnerability, seems trivial?
nightpool 119 days ago [-]
The author already had basically full Clickhouse querying abilities, and Clickhouse lets you run arbitrary SQL on postgres, the fact that the author used a read-only command to execute it wasn't the author bypassing a security boundary (anyone with access to the Clickhouse DB also had access to the Postgres DB), it was just a gadget that made the SSRF more convenient. They could have escalated it into a different internal HTTP API instead.
wtfse 119 days ago [-]
That being said, having the ability to send HTTP requests to the internal servers is usually not critical vulnerability. Therefore having Clickhouse low-severity escaping vulnerability actually lead the whole chain to reach code execution. All the other services were requiring me to send special headers, which is not possible most of the SSRF cases :(
nightpool 118 days ago [-]
I see what you're saying, but IMO the actual vulnerability there is that Clickhouse (by default?) was exposed fully unauthenticated and without any header requirement. Allowing completely unauthenticated access to Clickhouse, even read-only, means that they're just asking for issues like this.
ch2026 119 days ago [-]
Sure, it’s a bug they can fix. But it’s more the setup itself that’s the issue. For example clickhouse’s HTTP interface would normally require user/pass auth and not have access to all privileges. Clickhouse has a table engine that maps to local processes too (eg select from a python process you pipe stdin into).
No need for postgres if you have a fully authenticated user.
wtfse 119 days ago [-]
hey this is the author. Thanks for everyones comment here guys.
There as a actually a vulnerability Clickhouse, which helps you to execute any query on the remote postgresl. By default, you can't execute any random query! This bug was seperately reported to the Clickhouse and has been fixed seperately https://github.com/ClickHouse/ClickHouse/pull/74144/commits/...
Out of interest, how much does ZDI pay for a bug like this?
rs_rs_rs_rs_rs 119 days ago [-]
They probably don't accept something like this. Not that many Posthog self-hosted instances out there...
lkt 119 days ago [-]
That's what I thought too, but the article says it was submitted to ZDI and they handled the communication with Posthog
wtfse 119 days ago [-]
All of these vulnerabilities accepted by ZDI.Feel free to search the following codes. ZDI-CAN-25351. ZDI-CAN-25352. ZDI-CAN-25350. ZDI-CAN-25358.
anothercat 119 days ago [-]
Does this require authenticated access to the posthog api to kick off? In that case I feel clickhouse and posthog both have their share of the blame here.
nightpool 119 days ago [-]
It looks like the entire class of bugs here are "if you have access to Posthog's admin dashboard, you can configure webhook URLs that hit Posthog's internal services". That's not particularly surprising for a self-hosted system like the author's, but I expect it would pretty bad if you were using their cloud-hosted product.
anothercat 119 days ago [-]
Ah of couse! I forgot about the cloud hosted option.
> As it described on Clickhouse documentation, their API is designed to be READ ONLY on any operation for HTTP GET As described in the Clickhouse documentation, their API is designed to be READ ONLY on any operation for HTTP GET requests.
wtfse 119 days ago [-]
hi, this is the author of the article. Thanks for the feedback mate. fixed it.
yellow_lead 119 days ago [-]
Thanks! Great article
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taw_1265 119 days ago [-]
PostHog does a lot of vibe coding, I wonder how many other issues they have.
Nextgrid 119 days ago [-]
Not that I’m disproving it but do you have a source? Companies say all kinds of things for hype and to attract investors, but it doesn’t necessarily make it true.
matmuls 119 days ago [-]
looking at their commits, there are about 300+ commits tagged with " Generated with https://claude.com/claude-code" attribution.
dewey 119 days ago [-]
Just because AI tools are involved doesn't mean it's "Vibe coding".
somat 119 days ago [-]
If you leave "Generated with claude-code" in the commit message, It was vibe coded.
hsbauauvhabzb 119 days ago [-]
It sure is a pretty good indicator, and if you underestimate human laziness you’re gonna have a bad time regardless.
jwpapi 119 days ago [-]
Also looking at how much they’ve released and how fast and how they blog like they own the world (or design the website)
I used to look up to Posthog as I thought, wow this is a really good startup. They’re achieving a lot fast actually.
But turns out a lot was sloppy. I don’t trust them no more and would opt for another platform now.
Unfortunately a lot of people think it means any time an LLM helps write code, but I think we're winning that semantic battle - I'm seeing more examples of it used correctly than incorrectly these days.
It's likely that the majority of code will be AI assisted in some way in the future, at which point calling all of it "vibe coding" will lose any value at all. That's why I prefer the definition that specifies unreviewed.
chrisweekly 119 days ago [-]
I share your preference. (I also mourn the loss of the word "vibe" for other contexts.) In this case there were apparently hundreds of commit messages stating "generated by Claude Code". I feel like there's a missing set of descriptors -- something similar to Creative Commons with its now-familiar labels like "CC-BY-SA" -- that could be used to indicate the relative degree of human involvement. Full-on "AI-YOLO-Paperclips" at one extreme could be distinguished from "AI-IDE-TA" for typeahead / fancy autocomplete at the other. Simon, you're in a fantastic position to champion some kind of basic system like this. If you run w/ this idea, please give me a shout-out. :)
bopbopbop7 119 days ago [-]
I also hope that majority of the code in the future is AI assisted like it is with PostHog because my cyber security firm is going to make so much money.
danr4 119 days ago [-]
Very nice write up!
wtfse 119 days ago [-]
I'm glad you liked it mate.
Rendered at 05:55:19 GMT+0000 (UTC) with Wasmer Edge.
It's worth noting that at the time of this report, this only affected PostHog's single tenant hobby deployment (i.e. our self hosted version). Our Cloud deployment used our Rust service for sending webhooks, which has had SSRF protection since May 2024[1].
Since this report we've evolved our Cloud architecture significantly, and we have similar IP-based filtering throughout our backend services.
[0] https://github.com/PostHog/posthog/pull/25398
[1] https://github.com/PostHog/posthog/commit/281af615b4874da1b8...
What an elegant, interesting read.
What I don't quite understand: Why is the Clickhouse bug not given more scrutiny?
Like that escape bug was what made the RCE possible and certainly a core DB company like ClickHouse should be held accountable for such an oversight?
No need for postgres if you have a fully authenticated user.
There as a actually a vulnerability Clickhouse, which helps you to execute any query on the remote postgresl. By default, you can't execute any random query! This bug was seperately reported to the Clickhouse and has been fixed seperately https://github.com/ClickHouse/ClickHouse/pull/74144/commits/...
> As it described on Clickhouse documentation, their API is designed to be READ ONLY on any operation for HTTP GET As described in the Clickhouse documentation, their API is designed to be READ ONLY on any operation for HTTP GET requests.
I used to look up to Posthog as I thought, wow this is a really good startup. They’re achieving a lot fast actually.
But turns out a lot was sloppy. I don’t trust them no more and would opt for another platform now.
Unfortunately a lot of people think it means any time an LLM helps write code, but I think we're winning that semantic battle - I'm seeing more examples of it used correctly than incorrectly these days.
It's likely that the majority of code will be AI assisted in some way in the future, at which point calling all of it "vibe coding" will lose any value at all. That's why I prefer the definition that specifies unreviewed.