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Sondeon

For the CTO and the head of security

API security audit and security audit of your backend Your API responds and the app works. What else is it handing over?

We review the backend (the part of the system that runs on the server and nobody sees) and the API your team built with AI. You get what it exposes, what it protects and what to fix first.

You get the route inventory and each finding with its evidence. Scope and timeline are in writing before we start.

A man seen from behind, in a black T-shirt, works with code on a laptop in front of a translucent panel of warm light

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Who it is for

  • Your API stores or returns customers' personal data
  • Your team wrote the backend with AI and nobody has gone over it
  • A customer asks how you protect their data

You don't need it if your system publishes no API and stores no third-party data. And today we review Python APIs built with FastAPI.

Data leaks out through the backend

The screen only shows what the design asks for, but the API may be handing over much more. Someone who wants your data calls the API directly, without going through your app. In a Veracode lab benchmark (spring 2026), 45% of coding tasks completed with AI without security instructions came out with a known security flaw. Veracode sells security analysis.

45%

AI coding tasks with a known security flaw

Veracode, 2026

What your API exposes and what it protects: what this security audit looks at

  • Excess fields in responses (OWASP API3)
  • Functions without access control (OWASP API5)
  • Inventory of published routes (OWASP API9)
  • Endpoint contract and catalog (the API's addresses)
  • Security headers
  • Blocking of probes and fake crawlers
  • Personal data in logs

More than 150 control points

Technologies covered

  • Python
  • Node.js

Trademarks and logos belong to their respective owners. Their use here is descriptive only and implies no commercial relationship or sponsorship.

How it works

  1. Meeting and written scope

    In 30 minutes we look at what API you have and what data passes through it. Then you get in writing what is reviewed, against which environment and the timeline.

  2. Review of what the API publishes

    We look at what your API really publishes, as well as what the code says: routes, response fields, access control, headers and logs.

  3. Report and results meeting

    You get the route inventory and each finding with its evidence, and we go through it with your team. Each finding says how to check it.

What we need from you

  • The API's address and its documentation, if it exists
  • Read access to the backend repository
  • A test account for each type of user

How we work

What you get

  1. Route inventory, including the unprotected ones
  2. List of responses that expose excess data
  3. Technical report: each finding with its evidence and its priority
  4. One-page executive summary for leadership

How a finding arrives

Priority: High

The profile route returns other users' email and phone number

Where
API, profile route
Evidence
A request with another user's identifier returns their data
Impact
Personal data leak

An example of the report format, not a client's.

Shall we talk about your case?

A 30-minute meeting to see what you have and what to review first.

Book a free meeting

Expert review, automated tool or the AI itself

All three are useful, each for one thing. AI brings the volume and people bring the judgment: that is why our review uses an automated AI tool and senior developers supervise it.

See the full comparison

Hands drawing a diagram of screens joined by arrows with a marker on a small whiteboard, next to white headphones

Who reviews

The review is done by a team of senior developers, with many hours of development and of finding the mistakes AI makes when it codes. We know more than 1,200 review points. The automated AI tool goes through them, and people verify, direct and review.

Team of senior developers

José María Salido, founder of Sondeon, answers for it

  • AI brings the volume: it goes through the known review points
  • People bring the judgment: they verify every finding before it goes into the report
  • The result is explained in a meeting with your team
Who answers for it: José María Salido, on LinkedIn

Frequently asked questions

What is an API security audit, and what does it include?

It compares what your API exposes with what it should expose: unprotected routes, excess data in responses, headers and logs. Our health check covers Python APIs built with FastAPI and the server that publishes them, together with the app or website that uses them.

What is the difference between this review and a pentest?

A pentest tries to get into your system the way an outsider would. This review walks through what your API publishes and compares it with what it should publish: routes, fields, access, headers and logs. It does not replace a pentest.

Does the report count as compliance evidence?

It works as technical evidence of what was reviewed and what was found, with its date. It does not attest compliance with any standard and does not replace legal advice.

What do you need to review the API, and can it be done without affecting production?

The API's address, read access to the backend repository and a test account for each type of user. The review looks and measures: we change nothing in production without your approval, and all of it is written into the scope.

Do you fix the vulnerabilities you find in the API?

Yes, if you ask us to. The diagnosis comes first: each finding with its evidence and its priority. The fix is separate and only happens if you request it, and your team can also do it with the list in hand.

How much does an API security audit cost?

The 30-minute meeting is free. The rest depends on the number of routes in the API and on how many types of user have to be tested. We go over it in that meeting, and you get the scope and timeline of our health check in writing before we start.

Other services

  • Mobile app review

    Flutter apps built with AI, tested on real iOS and Android phones by command and with touch gestures, together with their backend.

  • Public website review

    Your website's performance, visibility in search engines and in AI assistants (SEO and GEO), accessibility and security, measured on the real page.

  • Database review

    PostgreSQL, Redis, Elasticsearch and RabbitMQ, in read-only mode: structure, indexes, slow queries, locks and connections.

  • Deployment server review

    The server your system will run on, reviewed before you go live: who has access, what runs on it and which limits break as you grow.

  • Infrastructure monitoring

    The Linux machines your system runs on, measured every few seconds, so you see a full disk or a stopped container before your users do.

  • API monitoring

    Every call to your API measured, with its latency, its error and the screen that requested it, so you know which endpoint to optimize before traffic grows.

All services

Request your free meeting

Fill in the form and we email you to set a day and a time. It is 30 minutes to see what you have and what to review first.

What should we control?

We use your details to answer your request, to be able to prove we received it and to protect the form. The privacy policy explains it in detail.