In enterprise development, there is often a temptation to take the path of least resistance for the sake of speed. "Why overcomplicate the database schema if incremental IDs work out of the box?" or "Who would even think to poke around inside the mobile client's internals?".
As a security researcher, I often see these "simple" decisions becoming the foundation for major data breaches. In today's world, traffic analysis and app decompilation tools are so accessible that finding vulnerabilities is no longer reserved for the elite. Now, it’s just a matter of a few spare hours.
1. The Trap of Numeric Identifiers
Imagine a payment service where a transaction is accessible at api/payments/100500. Any user can simply change the number to 100501. If the system lacks strict object-level authorization for every single record, they will see someone else's data.
This is a classic architectural flaw. Using UUIDs instead of standard integers is not an "extra"; it is a baseline standard. Predicting or brute-forcing a 128-bit identifier is practically impossible, whereas a numeric sequence is an open door for automated data scraping.
2. Email as a Leakage Point
Systems are often designed such that knowing just an email address reveals too much about a user.
-
The Error: A login or password recovery form that explicitly states: "User with this email is not registered."
-
The Risk: An attacker can use existing leaked databases to "ping" your service and compile a list of your actual clients. This is subsequently used for targeted phishing that looks frighteningly authentic.
3. Secrets in the User's "Pocket"
Many developers still believe that compiled mobile app code is a secure vault. They hardcode keys for subscription verification, API keys, or even secrets for signing requests directly into the code.
This is an illusion of security. There are publicly available methods that allow anyone to deconstruct a mobile app into its original components and extract all string constants. Any secret stored on the client side will eventually be discovered. If your authorization or authenticity checks happen only within the app without server-side validation, you have no security.
The Price of Negligence: Reputation and Fines
A data breach today is not just a blow to a reputation that takes years to recover; it is a direct threat to a company's financial stability.
Statistics and Reality
Over the past year, the number of personal data incidents has continued to rise. According to regulators, the financial and retail sectors remain at maximum risk. Moreover, over 60% of leaks are directly related to flaws in API design and improper access control configurations.
FAQ: Answers to Critical Questions
Q: Why can't we just use ID filtering on the backend?
A: You can, but it requires perfect discipline from every developer on every single endpoint. UUIDs, on the other hand, provide "security by default": even if an authorization check is missed somewhere, an attacker won't be able to guess another user's ID.
Q: How do I protect a mobile app if I can't store keys in the code?
A: All critical logic and authorization checks must reside on the server. The mobile app should only be an interface. To store temporary tokens on the device, use only system-provided secure storage.
Q: How fast do hackers find these vulnerabilities?
A: Using automated scanners and scripts that check for typical API architecture flaws, finding a vulnerability takes anywhere from a few minutes to a couple of hours. It doesn't require deep expertise - the tools do the work.
Q: What should we do if we discover a security gap?
A: Immediately close the vulnerability and conduct an audit of your logs to determine if any data was compromised. By law, you have a very limited window (24–72 hours) to notify the regulator; otherwise, penalties for concealing the incident will be added to the fines for the leak itself.
Design your systems so that data remains secure even if an attacker knows exactly how they are built.
