Research shows that hackers may hijack online accounts before users even register them by exploiting flaws that have since been fixed on popular websites such as Instagram, LinkedIn, Zoom, WordPress, and Dropbox.

Andrew Paverd, a researcher at Microsoft Security Response Center, and Avinash Sudhodanan, an independent security researcher, studied 75 popular online services and discovered that at least 35 are high-risk for account pre-hijacking attacks.

These attacks differ in type and severity, but they all emanate from poor security practices of the websites concerned.

“The impact of account pre-hijacking attacks is the same as that of account hijacking. Depending on the nature of the target service, a successful attack could allow the attacker to read/modify sensitive information associated with the account such as messages, billing statements, usage history, etc. or perform actions through the victim’s online identity,” said Sudhodanan. 

A hacker makes an account on a vulnerable site via a user’s email address and hopes that the victim labels it as spam. The hacker then waits for the victim to create an account on the site or indirectly tricks them into creating one.

In the process, there are five different attacks that hackers can perform, namely the classic-federated merge (CFM), the unexpired session (US) ID, the trojan identifier (TID), the unexpired email change (UEC), and the non-verifying Identity provider (IdP) attack (NV).

Among the five, research shows that the unexpired session is the most common type of attack.

Majority of online services today require new users to verify ownership of the email address. Hence, making new accounts using an individual’s email address will not proceed without access to the user’s email account.

To bypass this, the hacker can make the account using their email address and then switch to the victim’s email address, abusing a common functionality present in most online services.

Examples of platforms in high-risk for such attacks include Dropbox (UEC), Instagram (TID), LinkedIn (US), WordPress.com (US and UEC), and Zoom (CFM and NV).

To help mitigate this kind of attack, users are advised to set up multi-factor authentication on their accounts as soon as possible, as this would cause all past sessions to be invalidated.