Home Cyber Security News Bug Hunter Nets $15K Bounty For Discovering Exposed User Credentials in Paypal

Bug Hunter Nets $15K Bounty For Discovering Exposed User Credentials in Paypal

by Abeerah Hashim
PayPal XSS vulnerability

PayPal has confirmed a bug in its website that could expose users’ email addresses and passwords. Considering the seriousness of the vulnerability, PayPal even awarded a $15K bounty to the researcher for reporting the flaw.

PayPal Bug Exposing Credentials

Researcher Alex Birsan found a serious bug in the PayPal website. As described in his blog post, the vulnerability existed in the login form of PayPal. Hence, it posed a serious threat to the integrity of users’ data.

According to the researcher, he found a CSRF token and session ID in PayPal’s main authentication flow. His testing attempts made him realize the system’s resilience to classic CSRF attacks. However, further digging around revealed a bug in PayPal’s security challenge – a protection mechanism against brute force attacks.

In brief, he found that the problem existed with the reCAPTCHA challenge implemented on the login form which comes into action after a few failed login attempts. As stated in his post,

Upon detecting a possible brute-force attempt, the response to the next authentication attempt is a page containing nothing but a Google captcha. If the captcha is solved by the user, an HTTP POST request to /auth/validatecaptcha is initiated.

The request body already contained “familiar _csrf and _sessionID”. Completing the validation request then landed the user to the authentication flow with a self-submitting form that included the user’s email address and password in plain text.

I realized that, with the correct timing and some user interaction, knowing all the tokens used in this request was enough to get the victim’s PayPal credentials. In a real-life attack scenario, the only user interaction needed would have been a single visit to an attacker-controlled web page.

Birsan has also shared the proof-of-concept for the exploit in his post.

Researcher Won $15K Bounty

Upon finding the bug, the researcher collaborated with PayPal via their HackerOne bounty program. As revealed through the HackerOne report, Birsan found this vulnerability in November 2019. Then, with continued communication, PayPal eventually resolved the bug in December 2019. And, the disclosure came just recently.

As confirmed by PayPal,

A bug was identified whereby sensitive, unique tokens were being leaked in a JS file used by the recaptcha implementation…
PayPal implemented additional controls on the security challenge request to prevent token reuse, which resolved the issue, and no evidence of abuse was found.

PayPal has not only confirmed the presence of the bug but has also awarded a bounty of $15,300 to the researcher.

Let us know your thoughts in the comments.

You may also like

Latest Hacking News

Privacy Preference Center

Necessary

The __cfduid cookie is used to identify individual clients behind a shared IP address and apply security settings on a per-client basis.

cookie_notice_accepted and gdpr[allowed_cookies] are used to identify the choices made from the user regarding cookie consent.

For example, if a visitor is in a coffee shop where there may be several infected machines, but the specific visitor's machine is trusted (for example, because they completed a challenge within your Challenge Passage period), the cookie allows Cloudflare to identify that client and not challenge them again. It does not correspond to any user ID in your web application, and does not store any personally identifiable information.

__cfduid, cookie_notice_accepted, gdpr[allowed_cookies]

Advertising

DoubleClick by Google refers to the DoubleClick Digital Marketing platform which is a separate division within Google. This is Google’s most advanced advertising tools set, which includes five interconnected platform components.

DoubleClick Campaign Manager: the ad-serving platform, called an Ad Server, that delivers ads to your customers and measures all online advertising, even across screens and channels.

DoubleClick Bid Manager – the programmatic bidding platform for bidding on high-quality ad inventory from more than 47 ad marketplaces including Google Display Network.

DoubleClick Ad Exchange: the world’s largest ad marketplace for purchasing display, video, mobile, Search and even Facebook inventory.

DoubleClick Search: is more powerful than AdWords and used for purchasing search ads across Google, Yahoo, and Bing.

DoubleClick Creative Solutions: for designing, delivering and measuring rich media (video) ads, interactive and expandable ads.

doubleclick

Analytics

The _ga is asssociated with Google Universal Analytics - which is a significant update to Google's more commonly used analytics service. This cookie is used to distinguish unique users by assigning a randomly generated number as a client identifier. It is included in each page request in a site and used to calculate visitor, session and campaign data for the sites analytics reports. By default it is set to expire after 2 years, although this is customisable by website owners.

The _gat global object is used to create and retrieve tracker objects, from which all other methods are invoked. Therefore the methods in this list should be run only off a tracker object created using the _gat global variable. All other methods should be called using the _gaq global object for asynchronous tracking.

_gid works as a user navigates between web pages, they can use the gtag.js tagging library to record information about the page the user has seen (for example, the page's URL) in Google Analytics. The gtag.js tagging library uses HTTP Cookies to "remember" the user's previous interactions with the web pages.

_ga, _gat, _gid