Update Cart on Checkout is operated by add-ons.org.
The app stores the merchant's settings: how the quantity and remove controls look, what they say, which products, collections and tags they apply to, and which customer groups see them. It reads the shop's name, currency, domain and plan, the number of orders placed in the current month (a count only; no order is read), the products of the chosen collections and the products carrying the chosen tags, and, when the merchant limits the controls to customers with a tag, the tags of the logged-in customer. It writes the published settings to an app-owned shop metafield and a small app-owned metafield on each chosen product, so the checkout can read them without calling the app.
When a customer changes a quantity or removes an item at checkout, the app records the product, the variant, the old and new quantity and the time. It does not record who made the change: no name, email, address or customer id is stored. These numbers are shown to the merchant on the app's dashboard for the last 30 days and deleted after 90 days.
The app holds no personal data, so a customer's data request or erasure request received from Shopify (customers/data_request, customers/redact) has nothing to return or remove. A shop's data erasure request (shop/redact, 48 hours after uninstall) deletes everything stored for that shop.
Paid plans are billed by Shopify through the merchant's Shopify invoice. The app never sees payment details.
Data is exchanged with Shopify only. No other service receives store or customer data.
Settings remain until the merchant changes them, or until the app is uninstalled and Shopify requests shop data erasure, at which point everything for that shop is deleted. Authentication sessions are deleted on uninstall.
For privacy questions, use the contact form.