PayPal has plugged a huge hole that exposed every account to hijacking.
The cross-site request forgery (CSRF) flaw reported by Egyptian researcher Yassar H Ali allowed attackers access to any PayPal account of their choosing if they were capable of convincing a target to click a link.
A PayPal spokesperson confirmed the flaw to Vulture South adding it had no evidence accounts had been compromised.
"Through the PayPal Bug Bounty Program, one of our security researchers recently made us aware of a way to bypass PayPal's Cross-Site Request Forgery (CSRF) Protection Authorization System when logging onto PayPal.com," the spokesperson said. "Our team worked quickly to address this vulnerability, and we have already fixed the issue."
The "single-click" hack allowed attackers to link their email addresses to victim accounts, reset passwords and overtake accounts because Paypal authentication tokens were made reusable.
Cross-site request forgeries were common attacks against authenticated website victims that handed bad guys the capabilities of log in users such as password changes and fund transfers.
Ali earned US$10,000 for the disclosure and said the captured authentication token was valid for all PayPal accounts.
"After a deep investigation I found out that the CSRF auth is reusable for a specific user email address or username," Ali said in an advisory.
"This means attackers who found any of these CSRF tokens can [imitate] any logged in user.
[Attackers] can obtain the CSRF auth by intercepting the POST request from a page that provides an auth token before the logging-in process."
The researcher published a proof of concept video showcasing the now closed attack vector. ®