Here is a summary of the key points from the blog post in complete sentences:

The blog post is the third in a series about hacking AWS Lambda functions. This article highlights the importance of proper token validation in serverless architectures, especially when using Amazon Cognito. It emphasizes the need for multiple security layers, including API Gateway authorizers and server-side token validation, to protect against unauthorized access and data exposure.

The post examines a Cognito access token, which is in JSON Web Token (JWT) format. The token consists of a header, payload, and signature. By manipulating the payload, an attacker could access another user’s order data, bypassing authentication.

Initially, the example DVSA application lacked an API Gateway authorizer, allowing token manipulation. By adding a Cognito Authorizer in the API Gateway, it correctly validates the token signature, addressing the vulnerability. An alternative solution would be implementing token signature validation within the Lambda function code itself.

The key takeaways are the importance of proper token handling and validation at multiple levels, using tools like API Gateway authorizers an