PayPay - pay with your phone

Japan is famous for it’s love for cash and the people are very reluctant to use anything else. The government even had a 2-5% cashback program on most cashless payments in 2019-2020 to change this. Even after this, credit cards are often not accepted, especially at smaller shops or restaurants. On the other hand Japan has a handful of barcode-based mobile payment solutions: PayPay, LinePay, auPay, RakutenPay, FamiPay, MerPay etc., out of which PayPay seems to be the most widely accepted (in my experience).

Coke ON - buy from vending machines with your phone

Japan is full of drink vending machines:

However I don’t like coins. The vending machines at the train stations usually accept Suica, but elsewhere they are mostly cash only. Or that’s what I thought.

Meet Coke ON, the fun and reasonable (🤨) Coca-Cola official app, which lets you buy drinks from selected vending machines using your phone, paying with credit card, PayPay or LinePay. Moreover you get stamps for each purchase, that gets you a free drink after 15 stamps.

Open-redirect to XSS

Open redirects are generally treated as a low risk issue, due to the limited impact (more convincing phishing). However in certain cases a simple open redirect vulnerability can lead to reflected XSS, which I’ll talk about in this post.

Redirecting in a browser can happen in two ways:

1. The browser gets a 30x HTTP response code (e.g. 302 Found) with the destination of the redirect in the Location header
2. The JavaScript running on a site does the redirect by e.g. window.location.href='https://example.com' or window.location.assign('https://example.com'); or window.location.replace('https://example.com');

If an open redirect vulnerability exist with the second type of redirect, it might be an XSS as well using the javascript: pseudo-protocol. E.g. the following JavaScript code will pop up an alert:

url = "javascript:alert(document.domain)"; // coming from the user in real life
window.location.href= url;

Demo

Cross-app Scripting in Android apps

If an Android app accepts Intents to open a URL in a WebView, then a malicious app installed on the same device might open a javascript:alert(1)-like URL, which will run the provided JavaScript in the context of the victim app’s site (that is currently loaded in the WebView). This vulnerability is called Cross-app Scripting.

Restricting Google App Script permissions

Google Apps Script is a rapid application development platform that makes it fast and easy to create business applications that integrate with Google Workspace. You write code in modern JavaScript and have access to built-in libraries for favorite Google Workspace applications like Gmail, Calendar, Drive, and more.

https://developers.google.com/apps-script/overview

Google Apps Script provide an easy way to automate repetitive tasks in the Google ecosystem (e.g. Drive). It is somewhat similar to macros in Microsoft Office. An App Script will ask for permissions before it can interact with any document of the user, and by default these permissions are unnecessarily wide. This write up is meant to help restricting these permissions.