Security

How you sign in

• You sign in with your YSNOne account (OneAccount). Presupeso has no password screen and stores no passwords.
• Your session lives in a cookie that the browser doesn't let page scripts read (httpOnly) and that doesn't travel to other sites (SameSite).
• When you sign out, your YSNOne session is closed too, so the next «Sign in» doesn't let you in without asking.

How your data travels and is stored

• Everything travels encrypted over HTTPS.
• Your AI keys are stored encrypted with AES-256-GCM. After you add them only their last four characters are visible, to the team as well.
• Money is stored as whole numbers, without floating-point decimals, and balances are always calculated from transactions: there's no separate balance that can drift.
• Every change leaves a line in your budget's change log: what, when, who and through which door (the app, the assistant, a connected AI or another YSNOne app).

How the app is protected

• A strict content security policy: the browser only runs Presupeso's own code, with no third-party scripts or code from other domains.
• Every form and action carries a token against cross-site request forgery (CSRF) and its origin is checked.
• Incoming data is cleaned so it can't turn into a dangerous database query.
• A request limiter cuts off mass attempts.
• Errors don't reveal internal details: you get a sentence; the detail stays in our log.

Your AI, with permission and with limits

• Claude, ChatGPT or another AI connect over MCP with OneAccount OAuth: you authorize it with your account and never give it a password or a key.
• Each token is checked with OneAccount and must be issued for Presupeso: one issued for another app doesn't work here.
• Your AI only sees your budget. You can set it to read only or turn it off in settings, and remove the connection from the AI itself.
• Delicate actions take two steps: the AI shows you what will happen and it only goes ahead with your yes, using a code that expires in ten minutes and isn't valid if the data changes.
• What arrives from another YSNOne app can stay to review until you approve it, and it's never duplicated.

What the YSNOne team sees

The rule is count, don't read. The team's console shows how many people use Presupeso, how many transactions are recorded per channel, subscription status and AI usage. There's no screen with a person's transactions, balances or categories, and the team's AI can't see them either. Only team members with a verified email can open the console.

What we don't do

• We don't connect to your bank or ask for its passwords.
• We don't store card details: payments go through the YSNOne Balance.
• We don't use your data for advertising or to train artificial intelligence.

What you can do

• Protect your YSNOne account and your email: they're the key to everything.
• Check from time to time which AIs you have connected and remove the ones you don't use.
• Don't share your AI keys and set a spending limit with your provider.
• Export your data now and then: it's your personal backup.

If you find a security flaw

Write to us at [email protected] with the details. We review it as a priority and tell you what we did. Please don't publish it or access other people's data while we fix it.