WHMCS Zero-Day vulnerability used against PureVPN

Hong Kong-based PureVPN faced problems this weekend, after someone used a Zero-Day vulnerability in WHMCS to send the networking firm's customers an alarming message. The rogue email stated that the VPN service was going to shutdown due to legal issues, and that customer information was handed over to the authorities.

[Source code and 2.9 million accounts raided by attackers in Adobe breach]

Addressed simply as "Dear Customer" the letter said that due to an incident, PureVPN would be closing accounts and were no longer able to run an anonymization service. In addition, it said the company "had to handover all [customer] information to the authorities."

The letter was signed by Uzair Gadit, the co-Founder of PureVPN, who took to his company's blog and Twitter on Saturday to dispute the claims it made. According to a second email delivered to customers, the cause for the letter was a vulnerability in WHMCS -- a platform used by many service providers like PureVPN, to manage user registrations and accounts, as well as billing and support.

"Preliminary reports suggest that we are hit with a zero day exploit, found in [WHMCS]...We are able to confirm that the breach is limited to a subset of registered users Email IDs and names," a blog post by PureVPN explained.

The WHMCS vulnerability was disclosed last week in versions 5.2.7 and 5.1.9. Moreover, proof-of-concept code for launching an SQL Injection attack spread to a few different exploitation-based forums and places like Pastebin. The flaw itself resides in dbfunctions.php (update_query), and requires that the attacker have an account on the system; something that is easily done considering the nature of WHMCS.

At issue is the fact that the script trusts any SQL update that has a value starting with AES_ENCRYPT. As it was explained to CSO, this was a case of missing input validation checks, a common (yet risky) coding error.

It's unclear if there are any other websites targeted by those responsible for the PureVPN compromise. CSO asked PureVPN, since given the nature of the vulnerability itself, if it can be disproved that the entire email database was accessed, but the company didn't respond to questions.

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