SaaS security for startupsSecure your SaaS before your first enterprise customer asks you to prove it.
You don't need a security team to know where your product could leak customer data. Map your app in an afternoon, find the few risks that really matter, fix those first, and answer the security questionnaire with evidence instead of guesses.
- Free plan, no credit card
- Built for teams without a security hire
- Export your risk register as a PDF
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2.1Do you perform threat modeling or design risk assessments?
Yes. Every product has a threat model, reviewed each quarter and before major releases.
Data flow diagram + attack trees -
3.4How is one customer's data kept separate from another's?
Ownership is checked in one authorisation layer. Tested by requesting every endpoint as a second customer.
Risk register, row 1: mitigated -
4.2Do you keep a risk register with owners?
Yes. Each risk is scored, has an owner and a treatment.
risk-register.pdf attached -
6.1How do you assess third-party providers?
Payments, email and AI providers are modelled as dependencies, with what we do if each one fails or is breached.
Trust boundary per provider
What does SaaS security for startups actually involve?
For a startup, SaaS security means knowing the handful of ways your product could leak customer data, lose it or be taken over, fixing the worst of them first, and being able to show a customer that you did. In practice that is a threat model of your app: a diagram of how data moves, the attacks that matter for your design, a scored list of risks with owners, and a plan you keep up to date as you ship.
Security becomes urgent the day someone asks for proof.
For most founders it isn't a breach that starts the work. It's a deal, an audit request or a due-diligence list. Each one asks the same underlying question: do you know your risks, and what are you doing about them?
An enterprise security questionnaire
Fifty to three hundred questions on risk assessment, data isolation, access control, vendors and incidents, usually with a deadline set by someone else's procurement team.
What you showYour threat model and a risk register PDF, so the answers point at evidence and the gaps come with a fix date.
"Do you have SOC 2?"
SOC 2 expects a documented risk assessment (criteria CC3.1 to CC3.4) that identifies threats to your system and how you respond to them. The audit takes months.
What you showA risk assessment tied to your real architecture, kept current as you ship. On Pro, each mitigation is mapped to the SOC 2 criteria it supports.
Investor due diligence
Security is now a standard line on diligence checklists: what data you hold, who can reach it, and what would happen if it leaked.
What you showOne diagram of where customer data lives and a ranked list of risks with owners. It answers the question in five minutes.
What founders usually get wrong
These come from our four example SaaS threat models, scored likelihood × impact out of 25. None needs an advanced attacker. Most are design decisions that are cheap to fix while your codebase is small.
| Risk | Score | First fix |
|---|---|---|
| Read another customer's data by changing an IDInvoicely, a simple web SaaS | 20 Critical | Check ownership in one shared authorisation layer, never per endpoint |
| AI retrieval skips the tenant filterLexibase, AWS + Bedrock | 20 Critical | Apply the tenant from the verified token in one retrieval function |
| Credential stuffing on loginInvoicely | 16 Critical | Rate limits, breached-password checks, two-factor sign-in |
| Bots run up the AI model billQuillpad, shared hosting + OpenAI | 16 Critical | Per-plan quotas, token limits and a hard budget on the API project |
| Download the .env file or a backup zipQuillpad | 15 High | Serve only the public folder; deny dotfiles and archives |
| Any Microsoft tenant can sign inTeamscope, Azure + Google Cloud | 15 High | Allow-list each customer's tenant ID |
| "Import from URL" reaches your cloud credentials (SSRF)Lexibase | 15 High | Fetch URLs from an isolated worker with no cloud role |
| A forged "payment succeeded" webhookInvoicely | 10 High | Verify webhook signatures and reject replays |
| Your deploy role trusts any GitHub repositoryLexibase | 10 High | Pin the trust policy to your repository and environment |
Your scores will differ, because they depend on your data, your customers and how you built the product. That's the point of modelling your own app rather than following a generic checklist. For a full walkthrough of one model, see a complete threat model, step by step.
Your first threat model in an afternoon
Start from a finished example that looks like your stack, not a blank page. You're editing, not inventing.
Open the closest example
It opens as a draft with the diagram, attack trees and scored risk register filled in.
10 minutesMake the diagram match your app
Rename and delete components, add what you run. The attack tree generator drafts trees from a threat dictionary for anything new, and you review them.
1 hourRescore and pick the top three
Adjust likelihood and impact for your product, give each risk an owner, and choose the three you'll fix this month.
1 hourExport the register
Download the risk register as a PDF for the questionnaire, the data room or your own roadmap.
5 minutes
Quillpad
An AI writing assistant: a Laravel app on one hosting plan with the OpenAI API, Stripe and SMTP email. 12 scored risks.
Lexibase
An AI document assistant: multi-tenant document Q&A on AWS with Bedrock, Cognito, ECS and a vector index. 10 scored risks.
Teamscope
A people analytics app: Entra ID sign-in on Azure and BigQuery and Vertex AI on Google Cloud. 10 scored risks.
Invoicely
A SaaS invoicing app: a framework app on a managed cloud with Postgres, Stripe and an admin console. 10 scored risks.
Not sure which to pick? Compare the examples by stack.
Start free. Upgrade when the questionnaires start.
Free
$0, no credit card
- Up to 3 forests (one per product or environment)
- Data flow diagrams and attack trees
- Attack tree generator from your diagram
- STRIDE, OWASP Top 10, LINDDUN and CAPEC
- Risk register with PDF export
- The four example SaaS threat models
Pro
$29 per user per month
- Standards mapping, including SOC 2, ISO 27001, NIST CSF 2.0 and OWASP ASVS
- The B2B SaaS Platform industry template
- Unlimited forests and team collaboration
- Full reports for customers and auditors
- Backups, one-click recovery and audit logs
What ThreatTree won't do for you
- It won't make you SOC 2 or ISO 27001 compliant. That takes your controls and an auditor. ThreatTree itself isn't certified either.
- It doesn't threat model automatically. It drafts attack trees from a threat dictionary, and your team decides what's real and how much it matters.
- It doesn't scan your code or your cloud. Pair it with the scanners you already use: they find bugs, the threat model finds design flaws.
SaaS security for startups, answered
What founders ask before the first security review.
Do startups need threat modeling?
Once you hold customer data, yes, and earlier is cheaper. The flaws that hurt SaaS startups most, such as one customer reading another's data or a support tool with full database access, are design decisions. They are quick to fix while the codebase is small and expensive after you have hundreds of customers. A first threat model takes an afternoon, not a project.
How do I answer a security questionnaire without a security team?
Answer from evidence, not from memory. Most questionnaires ask the same things: how you assess risk, how customer data is isolated, how you control access, how you vet vendors and how you handle incidents. A threat model with a scored risk register answers the first three directly, and you can attach the register as a PDF. Be honest about gaps and say when they will be fixed; buyers trust a dated plan more than a perfect score.
When does a startup need SOC 2?
Usually when enterprise or mid-market customers start asking for the report during sales, often the first time a deal stalls in security review. SOC 2 is an audit by a CPA firm, so it takes months. A threat model doesn't replace the audit, but it gives you the risk assessment SOC 2 expects (criteria CC3.1 to CC3.4) and evidence you can show customers while the audit is under way. See SOC 2 vs ISO 27001 if you're choosing between them.
Is ThreatTree free for startups?
The Free plan covers a startup's first threat models: up to 3 forests, data flow diagrams, attack trees, the attack tree generator, STRIDE, OWASP Top 10, LINDDUN and CAPEC, a risk register you can export as a PDF and four example SaaS threat models to start from. Pro is $29 per user per month, with free view-only seats, and adds standards mapping (including SOC 2, ISO 27001 and NIST CSF 2.0), team collaboration, full reports, backups and audit logs.
Will ThreatTree make my startup SOC 2 compliant?
No tool can. Compliance comes from your controls and an auditor's report. ThreatTree helps you find and prioritise risks, record the decisions and map mitigations to SOC 2 criteria on Pro, which is useful evidence. ThreatTree itself is not SOC 2 or ISO 27001 certified.
Know your biggest risks before your customers ask.
Free plan, no credit card. Open the example closest to your stack and have a first threat model by the end of the day.