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Disputed eBay platform vuln poses ‘severe risk’ to tat bazaar's users

Infosec bods warn of problem – and so far there's no reaction

A vulnerability in eBay’s online sales platform creates a mechanism for crooks to sling malware or run phishing campaigns.

The vulnerability allowed hackers to bypass eBay’s code validation mechanisms, thereby allowing them to push malicious Javascript code towards targeted eBay users. If the flaw is left unpatched, eBay’s customers will continue to be exposed to potential phishing attacks and data theft, Check Point warns.

The flaw in eBay’s platform was discovered by security researchers at Check Point and reported to eBay on 15 December 2015, followed by a PoC (proof of concept) and a description of the vulnerability details. However, on 16 January 2016, eBay stated that it has no plans to fix the vulnerability since it allows active content on its platform.

eBay does have security controls to handle active content. The marketplace reckons these controls are sufficient – an assessment disputed by the Check Point team. Security researchers reckon it’s possible to bypass eBay’s active content security policies and insert a malicious code to our seller page without any difficulty or restriction.

Check Point said the firm’s reluctance to fix the vulnerability prompted it to go public about the flaw on Tuesday.


Check Point security researcher Roman Zaikin warns that miscreants might abuse the unpatched flaw to execute malicious code on eBay users’ devices, using a non-standard technique called “JSF**k”.

eBay performs simple verification, but only strips alpha-numeric characters from inside the script tags. The JSF**k technique allows the attackers to get around this protection by using a very limited and reduced number of characters, Check Point explains.

To exploit the vulnerability, an attacker creates an online eBay store before uploading a maliciously crafted item description. eBay prevents users from including scripts or iFrames by filtering out those HTML tags. However, by using JSF**k, the attacker is able to create a program that will load an additional JavaScript code from his server.

The tactic would allow hackers to create a listings page that harbours malicious code. Customers could then be tricked into opening the page using a pop-up message on the attacker’s eBay store enticing the user into downloading a new eBay mobile application, by offering a one-time discount.

If a user taps the “download” button, they unknowingly download a malicious application to their device., and the code will be executed by the user’s browser or mobile app, opening the door to numerous cybercrime scams in the process raining from phishing to malware infection.

“The eBay attack flow provides cybercriminals with a very easy way to target users: sending a link to a very attractive product to execute the attack.,” said Oded Vanunu, security research group manager at Check Point. “The main threat is spreading malware and stealing private information. Another threat is that an attacker could have an alternate login option pop up via Gmail or Facebook and hijack the user’s account.”

Check Point has published a 30-second video to show the attack in action.

eBay commented: “As a company, we’re committed to providing a safe and secure marketplace for our millions of customers around the world. We take reported security issues very seriously, and work quickly to evaluate them within the context of our entire security infrastructure.” ®

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