Disclaimer ⚠️

The authors of this document take no responsibility for correctness. This project is merely here to help guide security researchers towards determining whether something is vulnerable or not, but does not guarantee accuracy. This project heavily relies on contributions from the public; therefore, proving that something is vulnerable is the security researcher and bug bounty program's sole discretion. On top of that, it is worth noting that some bug bounty programs may accept dangling DNS record reports without requiring proof of compromise.

What is a subdomain takeover?

Subdomain takeover vulnerabilities occur when a subdomain (subdomain.example.com) is pointing to a service (e.g. GitHub pages, Heroku, etc.) that has been removed or deleted. This allows an attacker to set up a page on the service that was being used and point their page to that subdomain. For example, if subdomain.example.com was pointing to a GitHub page and the user decided to delete their GitHub page, an attacker can now create a GitHub page, add a CNAME file containing subdomain.example.com, and claim subdomain.example.com.

You can read up more about subdomain takeovers here:

• https://labs.detectify.com/2014/10/21/hostile-subdomain-takeover-using-herokugithubdesk-more/
• https://www.hackerone.com/blog/Guide-Subdomain-Takeovers
• https://0xpatrik.com/subdomain-takeover-ns/

Safely demonstrating a subdomain takeover

Based on personal experience, claiming the subdomain discreetly and serving a harmless file on a hidden page is usually enough to demonstrate the security vulnerability. Do not serve content on the index page. A good proof of concept could consist of an HTML comment served via a random path:

$ cat aelfjj1or81uegj9ea8z31zro.html
<!-- PoC by username -->

Please be advised that this depends on what bug bounty program you are targeting. When in doubt, please refer to the bug bounty program's security policy and/or request clarifications from the team behind the program.

How to use this project

I recommend searching for the name of the service you are targeting in the issues tab. That way you can see the on-going discussion and more detailed steps on how to claim the subdomain you are after.

How to contribute

You can submit new services here: https://github.com/EdOverflow/can-i-take-over-xyz/issues/new?template=new-entry.md.

A list of services that can be checked (although check for duplicates against this list first) can be found here: EdOverflow#26.

All entries

Engine	Status	Fingerprint	Discussion	Documentation
Acquia	Not vulnerable	Web Site Not Found	Issue #103
Agile CRM	Vulnerable	Sorry, this page is no longer available.	Issue #145
Airee.ru	Vulnerable		Issue #104
Anima	Vulnerable	If this is your website and you've just created it, try refreshing in a minute	Issue #126	Anima Documentation
Akamai	Not vulnerable		Issue #13
AWS/S3	Vulnerable	The specified bucket does not exist	Issue #36
AWS/Load Balancer (ELB)	Not Vulnerable	status NXDOMAIN and CNAME pointing to XYZ.elb.amazonaws.com	Issue #137
Bitbucket	Vulnerable	Repository not found
Campaign Monitor	Vulnerable	Trying to access your account?		Support Page
Cargo Collective	Vulnerable	404 Not Found		Cargo Support Page
Cloudfront	Not vulnerable	ViewerCertificateException	Issue #29	Domain Security on Amazon CloudFront
Desk	Not vulnerable	Please try again or try Desk.com free for 14 days.	Issue #9
Digital Ocean	Vulnerable	Domain uses DO name serves with no records in DO.
Discourse	Vulnerable			Hackerone
Fastly	Edge case	Fastly error: unknown domain:	Issue #22
Feedpress	Not vulnerable	The feed has not been found.	Issue #80
Firebase	Not vulnerable		Issue #128
Fly.io	Vulnerable	404 Not Found	Issue #101
Freshdesk	Not vulnerable			Freshdesk Support Page
Gemfury	Vulnerable	404: This page could not be found.	Issue #154	Article
Ghost	Vulnerable	The thing you were looking for is no longer here, or never was
Github	Vulnerable	There isn't a Github Pages site here.	Issue #37 Issue #68
Gitlab	Not vulnerable		HackerOne #312118
Google Cloud Storage	Not vulnerable	NoSuchBucketThe specified bucket does not exist.
HatenaBlog	vulnerable	404 Blog is not found
Help Juice	Vulnerable	We could not find what you're looking for.		Help Juice Support Page
Help Scout	Vulnerable	No settings were found for this company:		HelpScout Docs
Heroku	Edge case	No such app	Issue #38
Instapage	Not vulnerable		Issue #73
Intercom	Vulnerable	Uh oh. That page doesn't exist.	Issue #69	Help center
JetBrains	Vulnerable	is not a registered InCloud YouTrack		YouTrack InCloud Help Page
Key CDN	Not vulnerable		Issue #112
Kinsta	Vulnerable	No Site For Domain	Issue #48	kinsta-add-domain
LaunchRock	Vulnerable	It looks like you may have taken a wrong turn somewhere. Don't worry...it happens to all of us.	Issue #74
Mashery	Edge Case	Unrecognized domain	HackerOne #275714, Issue #14
Microsoft Azure	Vulnerable		Issue #35
Netlify	Edge Case		Issue #40
Ngrok	Vulnerable	Tunnel *.ngrok.io not found	Issue #92	Ngrok Documentation
Pantheon	Vulnerable	404 error unknown site!	Issue #24	Pantheon-Sub-takeover
Pingdom	Vulnerable	Sorry, couldn't find the status page	Issue #144	Support Page
Readme.io	Vulnerable	Project doesnt exist... yet!	Issue #41
Sendgrid	Not vulnerable
Shopify	Edge Case	Sorry, this shop is currently unavailable.	Issue #32, Issue #46	Medium Article
SmartJobBoard	Vulnerable	This job board website is either expired or its domain name is invalid.	Issue #139	Support Page
Smartling	Edge Case	Domain is not configured	Issue #67
Squarespace	Not vulnerable
Statuspage	Not Vulnerable	Status page pushed a DNS verification in order to prevent malicious takeovers what they mentioned in This Doc	PR #105 and PR #171	Statuspage documentation
Strikingly	Vulnerable	page not found	Issue #58	Strikingly-Sub-takeover
Surge.sh	Vulnerable	project not found		Surge Documentation
Tumblr	Edge Case	Whatever you were looking for doesn't currently exist at this address
Tilda	Edge Case	Please renew your subscription	PR #20
Uberflip	Vulnerable	Non-hub domain, The URL you've accessed does not provide a hub.	Issue #150	Uberflip Documentation
Unbounce	Edge Case	The requested URL was not found on this server.	Issue #11
Uptimerobot	Vulnerable	page not found	Issue #45	Uptimerobot-Sub-takeover
UserVoice	Vulnerable	This UserVoice subdomain is currently available!
Webflow	Edge Case	The page you are looking for doesn't exist or has been moved.	Issue #44	forum webflow
Wordpress	Vulnerable	Do you want to register *.wordpress.com?
Worksites	Vulnerable	Hello! Sorry, but the website you’re looking for doesn’t exist.	Issue #142
WP Engine	Not vulnerable
Zendesk	Not vulnerable	Help Center Closed	Issue #23	Zendesk Support