Global online payments firm PayPal, which has around 137 million active users worldwide, has been alerted to a series of bugs in its software, including one that allows attackers to hijack its customers' accounts.
The security flaws were discovered through PayPal's bug bounty programme by researchers at Vulnerability Laboratory in Germany, which specialises in finding software threats.
The most serious problem allows remote attackers to inject their own malicious code into the Paypal e-commerce website content management system and API, and hijack a customer's account. The flaw is located in the software that verifies the identity of a customer receiving an online payment via their phone number ID. Vulnerability Lab says it can be patched by encoding the vulnerable input fields and the affected output mailing.
Other bugs discovered by the researchers include a client-side weakness in PayPal's official Chinese web application service, a persistent input validation vulnerability in the GP+ web app which supports its online sales stores, and a bug in its BillSAFE online payment service web application.
The GP+ and BillSAFE flaws allow remote attackers to inject their own malicious persistent script codes to compromise the apps. The bug in PayPal's Chinese web application service allows remote attackers to redirect the victim to an external malicious source or website.
PayPal entered the Chinese market in 2010 through an agreement with China UnionPay (CUP), the country's bankcard association, to allow Chinese consumers to use PayPal to shop online.
PayPal has issued a number of patches and updates for GP+ bugs in the second and third quarters of 2013. Vulnerability Lab's researchers have detailed patches for the other problems.
The bugs are the latest in a series of PayPal problems identified by the Vulnerability Lab research team this year – covering around 110 issues - operating through PayPal's bug bounty programme.
PayPal offers a scale of rewards for researchers who identify problems in its websites and apps, ranging from US$ 750 (£465) for cross-site scripting (XSS) and cross-site request forgery (CSRF) vulnerabilities, up to US$ 5,000 (£3,100) for SQL injection attacks and US$ 10,000 (£6,200) for remote code execution malware.
Benjamin Kunz Mejri (left), owner of Vulnerability Lab and Evolution Security Company, told SCMagazineUK.com that his researchers have earned between US$ 20,000 (£12,400) and US$ 50,000 (£31,500) in rewards through the PayPal bounty scheme in 2012 and 2013.
In response to this article, SCMagazineUK.com was told by Paypal's spokesperson "We appreciate the contributions that security researchers like Vulnerability Labs have made to PayPal's Bug Bounty Programme, and we have recognised them on our Wall of Fame for their efforts. We would like to confirm that we have fixed the web redirection, persistent input validation, and injection vulnerabilities that Vulnerability Labs originally reported. We can assure you that there is no evidence at this time that any PayPal customers have been impacted by the bug. We have given bounties to the Vulnerability Labs teams in thanks for their efforts to help us keep PayPal secure for our customers."