# Emails Vulnerabilities ## Payloads ### Ignored parts of an email The symbols: **+, -** and **{}** in rare occasions can be used for tagging and ignored by most e-mail servers * E.g. john.doe+intigriti@example.com → john.doe@example.com **Comments between parentheses ()** at the beginning or the end will also be ignored * E.g. john.doe(intigriti)@example.com → john.doe@example.com ### Whitelist bypass * inti(;inti@inti.io;)@whitelisted.com * inti@inti.io(@whitelisted.com) * inti+(@whitelisted.com;)@inti.io ### IPs You can also use IPs as domain named between square brackets: * john.doe@\[127.0.0.1] * john.doe@\[IPv6:2001:db8::1] ### Other vulns ![](<.gitbook/assets/image (296).png>) ## Third party SSO ### XSS Some services like **github** or **salesforce allows** you to create an **email address with XSS payloads on it**. If you can **use this providers to login on other services** and this services **aren't sanitising** correctly the email, you could cause **XSS**. ### Account-Takeover If a **SSO service** allows you to **create an account without verifying the given email address** (like **salesforce**) and then you can use that account to **login in a different service** that **trusts** salesforce, you could access any account.\ _Note that salesforce indicates if the given email was or not verified but so the application should take into account this info._ ## Reply-To You can send an email using _**From: company.com**_** ** and _**Replay-To: attacker.com**_ and if any **automatic reply** is sent due to the email was sent **from** an **internal address** the **attacker** may be able to **receive** that **response**. ## **References** * [**https://drive.google.com/file/d/1iKL6wbp3yYwOmxEtAg1jEmuOf8RM8ty9/view**](https://drive.google.com/file/d/1iKL6wbp3yYwOmxEtAg1jEmuOf8RM8ty9/view) ## Hard Bounce Rate Some applications like AWS have a **Hard Bounce Rate** (in AWS is 10%), that whenever is overloaded the email service is blocked. A **hard bounce** is an **email** that couldn’t be delivered for some permanent reasons. Maybe the **email’s** a fake address, maybe the **email** domain isn’t a real domain, or maybe the **email** recipient’s server won’t accept **emails**) , that means from total of 1000 emails if 100 of them were fake or were invalid that caused all of them to bounce, **AWS SES** will block your service. So, if you are able to **send mails (maybe invitations) from the web application to any email address, you could provoke this block by sending hundreds of invitations to nonexistent users and domains: Email service DoS.**