How i found a Email Spoofing vulnerability to perform Phishing Attacks

**Disclaimer: take permission man..it ain’t that hard**

As a penetration tester, Burp Suite is one of my go-to tools for performing manual web application testing. On this particular engagement, I was tasked with evaluating the security of an online application which provided advice to users using AI. The application allowed users to give a assessment which would generate a report and be sent through the email.

I began by using Burp Suite to intercept the traffic between my browser and the application’s backend. By enabling the proxy and setting up my browser to route traffic through Burp, I could capture all HTTP(S) requests.

NOW U MIGHT HAVE HEARD THAT AUTOMATION IS KING, BUT LET ME TELL U THAT MANUAL TESTING IS EVEN BETTER.

i had spent a few weeks along with a friend testing this website, but only on the surface..but only have going through the functionality of a user from start to the end, were we able to spot this hidden request.

(usually i would save the website as in scope and filter out the rest of the request from other endpoints.(THAT WAS THE MISTAKE)

Sometimes u need to see all the request that have been captured..as it might indirectly be hiding a vulnerability that could be exploited

the post request was somewhat like:

full request from burp

The first red flag was that the body was populated with an arbitrary email address—something like victim@gmail.com. There was no apparent validation or sanitization on this field. Even the other values in json body was completely exposed…allowing an attacker to send emails to multiple users with this own content(CAUSE IT ALLOWED SOME HTML INJECTION ALSO)

In essence, the application was taking whatever email address a user submitted in the request and sending it to them along with the content that the attacker provides

To confirm this, I decided to manipulate the field in my request.I also tested this with other emails, and it worked just as easily. This demonstrated a fundamental flaw in the application’s email handling logic: it was entirely trusting user input without any checks.

Email spoofing can have serious consequences for both individuals and organizations. Here’s why:

Phishing Attacks: Malicious actors can craft convincing emails that appear to come from trusted sources. For example, an attacker can spoof a bank’s email address, tricking users into clicking malicious links or downloading harmful attachments.Brand Reputation Damage: If an attacker spoofs a company’s official email address, it could lead to a loss of trust among customers. Users may begin ignoring legitimate emails, causing irreparable harm to the brand.Spam and Malware: Spoofed emails can also be used to distribute spam or malware. Because the email appears to come from a trusted source, it bypasses many spam filters and increases the likelihood of successful delivery.Social Engineering: Attackers can leverage the trusted appearance of a spoofed email to manipulate recipients into taking actions they otherwise wouldn’t, such as transferring funds or sharing sensitive information.

Upon discovering the vulnerability, I realized that it was essential to prevent users from being able to specify any content as the want. Below are some steps that the development team should take to mitigate the vulnerability:

The most important fix is to ensure that the message is sent from the server and from the client side.

Finally, it’s important for the application to log all email-sending activity and monitor for signs of abuse. For instance, if an email is sent from an unusual IP address or if there is an abnormal volume of emails being sent, the system can raise an alert for further investigation.

i could add other content,but the impact was already visible through the post request

Email spoofing vulnerabilities are not just a theoretical concern; they are very real and can lead to devastating consequences. In this case, I discovered a simple yet critical flaw that allowed attackers to forge email addresses through the frontend. By leveraging Burp Suite, I was able to identify and exploit this vulnerability, which could have been used for phishing, spamming, and other malicious activities.

Fortunately, I was able to report the issue to the development team, who immediately began working on a patch. As always, this discovery was a valuable reminder of the importance of securing user input and implementing proper validation mechanisms in web applications.

If you’re a web developer or a security researcher, always stay vigilant. Even seemingly minor vulnerabilities like email spoofing can have major consequences. Stay safe, and happy testing!