Insecure design is one of the most fundamental security risks in the OWASP Top 10, and a big inspiration for building Perceptive. But what exactly is it? Let’s take a look.

–

01 – What is insecure design?

Insecure design occurs when critical security controls are missing, ineffective, or not properly considered during the software development lifecycle (SDLC). It results from poor architectural decisions, weak risk assessments, or inadequate security controls.

Design flaws are some of the hardest security issues to fix – because by the time you realise they exist, they’re baked into the system.

Unlike insecure implementation (which can often be fixed by patching or rewriting code), an insecure design means fundamental security controls are missing or flawed – something that cannot be solved with quick fixes.

Some common causes of insecure design include:

• Lack of security risk profiling – Failing to assess business risks leads to weak security decisions.
• Missing of ineffective security controls – No validation of permissions, inadequate authentication, or poorly defined session management, for example.
• Failing to implement Secure by Design principles – Security controls are treated as add-ons rather than core components of development.
• No threat modelling – Attack scenarios are not considered, making systems easy to exploit.

Without security considerations at the design phase, applications become inherently vulnerable, no matter how they’re implemented.

It’s the exact reason we built Perceptive.

–

02 – How is insecure design exploited?

There are seemingly endless real–world examples of insecure design being exploited, from the Equifax breach in 2017 where a failure to patch an insecurely designed component led to the exposure of 147 million records, to the Mirai Botnet the previous year where millions of IoT devices were compromised due to hardcoded default credentials (a classic example of an insecure design choice).

Insecure design covers a lot of ways attackers take advantage of poorly designed security controls, but some of the obvious examples are:

• Authentication bypass – If an admin panel lacks proper access controls, an attacker might guess or force their way in.
• Session hijacking – Poorly designed session management could allow attackers to reuse valid session tokens.
• Business logic abuse – An attacker exploits flawed workflows to manipulate financial transactions or bypass purchase limits.
• Predictable identifiers – If user profiles are accessed via sequential IDs (e.g. id=123), an attacker could iterate through IDs to steal data.

Underpinning them all, at some point, an insecure design choice was made.

–

03 – How do you prevent Insecure Design?

** cough, cough ** “Use Perceptive!” – ok, but in all seriousness, a Secure by Design approach will help ensure security flaws don’t make it into production. Some tips:

• Incorporate threat modelling early – Identify potential risks before development begins.
• Enforce secure design principles – Apply Least Privilege, Defence in Depth, and Secure Defaults at all layers.
• Use strong authentication and access controls – Implement RBAC and MFA to enforce identity verification.
• Conduct regular security reviews – Peer code reviews, automated security scans, and pen tests can uncover design flaws before attackers do.
• Develop a security culture – Ensure security is built into processes, rather than treated as an afterthought.

–

Insecure design isn’t just another type of vulnerability – it’s a structural weakness. If you don’t bake security in from the start, fixing it later becomes difficult, expensive, or even impossible. The best defence? Secure by Design thinking from day one.