What is a data leak?
A data leak is private information becoming visible to people who were never meant to see it: user records, email addresses, messages, payment details, or the app's own credentials. Unlike a breach, which involves an attacker breaking in, a leak usually requires no attack at all; the data was simply left where others could reach it.
That's what makes leaks the signature risk of unreviewed code. Nothing has to go wrong for a leak to exist; it ships with the app, silently, until someone notices.
How do data leaks happen in vibe-coded apps?
A few patterns account for most incidents. Secrets end up in frontend code, where every visitor's browser can read them. Access control is missing, so any signed-in user can request any other user's records by changing an ID in the URL. Databases get created with permissive defaults that were never tightened. And logs or error messages echo sensitive values to whoever sees them.
None of these require a mistake by a user or a clever attacker, which is why they survive testing: the happy path works perfectly while the leak sits in plain sight.
How can builders prevent data leaks?
The defenses map one-to-one to the causes: secrets in environment variables and never in code the browser receives, access rules that check ownership on every data request, database permissions reviewed before launch, and logs kept free of sensitive values.
The habit that ties it together is asking for an audit before deploying: "check this app for exposed secrets, missing access control, and data any user could see that isn't theirs." The AI that wrote the code is genuinely good at finding these flaws when explicitly pointed at them.
