Defaults Can Sink You TL;DR: Treat unknown responses as unauthorized, not as valid. Problems Security risks
Ignoring unknown cases
Error Misinterpretation
Defaulting to valid states
Mismatch Authorizations
Failing to log events
Exploitation Potential Solutions Validate all responses against a closed set of known codes.
Default (and unknown) to unauthorized or Remove Defaults.
Log every mismatched or unexpected case for analysis.
Test with edge scenarios.
Synchronize response pools with processors regularly to avoid outdated codes.
Focus on security making it a shift left process.
Design systems with change resilience to handle evolving scenarios. Context Today is computer security day and every programmer needs to acknowledge its responsibility. Imagine an application handling sales that relies on response pools from credit card processors to handle transactions. Each credit card processor provides predefined response codes for various situations, such as insufficient balance or expired cards. The issue begins when a processor adds a new response code for denied transactions but doesn't notify the platform. The application doesn't recognize the new code, defaults to treating it as "not found," and authorizes the purchase. Users notice this flaw and exploit it to make unauthorized purchases. The platform's revenue plummets, leading to bankruptcy. Sample Code Wrong String response = paymentProcessor.authorize(cardDetails);

switch (response) {
    case "DECLINED_INSUFFICIENT_FUNDS":
        // Handle insufficient funds
        break;
    case "DECLINED_EXPIRED_CARD":
        // Handle expired card
        break;
    default:
        // Authorize purchase
        break;
} Right String response = paymentProcessor.authorize(cardDetails);

switch (response) {
    case "APPROVED":
        // Authorize purchase
        break;
    case "DECLINED_INSUFFICIENT_FUNDS":
        // Handle insufficient funds
        break;
    case "DECLINED_EXPIRED_CARD":
        // Handle expired card
        break;
    case "DECLINED_NEW_REASON":
        // Handle new declined reason
        break;
    default:
        // Reject purchase (default case for unknown responses)
        break;
} Detection [x]Manual You can detect this smell by reviewing error-handling logic. Check if the system logs and denies unrecognized cases. Automated tests can help identify if new or unexpected inputs default to valid actions. Static analysis tools can help by flagging potentially incomplete error handling. Tags Security Level [x]Intermediate Why Bijection Is Important It's critical to maintain a one-to-one correspondence between your application's internal representation of payment processor responses and the actual codes returned by the processor. When you break the Bijection, you create a mismatch. The application interprets unknown codes incorrectly, leading to unexpected behavior, security holes, and potentially disastrous business consequences. AI Generation AI tools can create this smell if you don't specify how to handle unknown cases. For example, generic error handling might default to benign outcomes like "not found" or "success." AI Detection AI generators can fix this smell when you instruct them to treat unknown cases as unauthorized and emphasize logging and testing unexpected scenarios. Try Them! Remember: AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini Conclusion Always handle unknown cases cautiously. Defaults like "not found" can lead to severe security issues and financial losses. Make logging and denying unknown responses part of your development practices. Make shift-left decisions related to security while programming. Relations https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-viii-8mn3352 Disclaimer Code Smells are my opinion. Credits Photo by Nathana Rebouças on Unsplash https://www.youtube.com/watch?v=J2QOejhA6ek Assumptions are the mother of all failures. Said Ouissal Software Engineering Great Quotes This article is part of the CodeSmell Series. How to Find the Stinky Parts of your Code Defaults Can Sink You Defaults Can Sink You TL;DR: Treat unknown responses as unauthorized, not as valid. TL;DR: Treat unknown responses as unauthorized, not as valid. Problems Security risks Ignoring unknown cases Error Misinterpretation Defaulting to valid states Mismatch Authorizations Failing to log events Exploitation Potential Security risks Ignoring unknown cases Error Misinterpretation Defaulting to valid states Mismatch Authorizations Failing to log events Exploitation Potential Solutions Validate all responses against a closed set of known codes. Default (and unknown) to unauthorized or Remove Defaults. Log every mismatched or unexpected case for analysis. Test with edge scenarios. Synchronize response pools with processors regularly to avoid outdated codes. Focus on security making it a shift left process. Design systems with change resilience to handle evolving scenarios. Validate all responses against a closed set of known codes. Default (and unknown) to unauthorized or Remove Defaults . Remove Defaults Log every mismatched or unexpected case for analysis. Test with edge scenarios. Synchronize response pools with processors regularly to avoid outdated codes. Focus on security making it a shift left process. Design systems with change resilience to handle evolving scenarios. Context Today is computer security day and every programmer needs to acknowledge its responsibility. computer security day Imagine an application handling sales that relies on response pools from credit card processors to handle transactions. Each credit card processor provides predefined response codes for various situations, such as insufficient balance or expired cards. The issue begins when a processor adds a new response code for denied transactions but doesn't notify the platform. The application doesn't recognize the new code, defaults to treating it as "not found," and authorizes the purchase. Users notice this flaw and exploit it to make unauthorized purchases. The platform's revenue plummets, leading to bankruptcy. Sample Code Wrong String response = paymentProcessor.authorize(cardDetails);

switch (response) {
    case "DECLINED_INSUFFICIENT_FUNDS":
        // Handle insufficient funds
        break;
    case "DECLINED_EXPIRED_CARD":
        // Handle expired card
        break;
    default:
        // Authorize purchase
        break;
} String response = paymentProcessor.authorize(cardDetails);

switch (response) {
    case "DECLINED_INSUFFICIENT_FUNDS":
        // Handle insufficient funds
        break;
    case "DECLINED_EXPIRED_CARD":
        // Handle expired card
        break;
    default:
        // Authorize purchase
        break;
} Right String response = paymentProcessor.authorize(cardDetails);

switch (response) {
    case "APPROVED":
        // Authorize purchase
        break;
    case "DECLINED_INSUFFICIENT_FUNDS":
        // Handle insufficient funds
        break;
    case "DECLINED_EXPIRED_CARD":
        // Handle expired card
        break;
    case "DECLINED_NEW_REASON":
        // Handle new declined reason
        break;
    default:
        // Reject purchase (default case for unknown responses)
        break;
} String response = paymentProcessor.authorize(cardDetails);

switch (response) {
    case "APPROVED":
        // Authorize purchase
        break;
    case "DECLINED_INSUFFICIENT_FUNDS":
        // Handle insufficient funds
        break;
    case "DECLINED_EXPIRED_CARD":
        // Handle expired card
        break;
    case "DECLINED_NEW_REASON":
        // Handle new declined reason
        break;
    default:
        // Reject purchase (default case for unknown responses)
        break;
} Detection [x]Manual [x] Manual [x] You can detect this smell by reviewing error-handling logic. Check if the system logs and denies unrecognized cases. Automated tests can help identify if new or unexpected inputs default to valid actions. Static analysis tools can help by flagging potentially incomplete error handling. Tags Security Security Level [x]Intermediate [x] Intermediate [x] Why Bijection Is Important It's critical to maintain a one-to-one correspondence between your application's internal representation of payment processor responses and the actual codes returned by the processor. When you break the Bijection , you create a mismatch. Bijection The application interprets unknown codes incorrectly, leading to unexpected behavior, security holes, and potentially disastrous business consequences. AI Generation AI tools can create this smell if you don't specify how to handle unknown cases. For example, generic error handling might default to benign outcomes like "not found" or "success." AI Detection AI generators can fix this smell when you instruct them to treat unknown cases as unauthorized and emphasize logging and testing unexpected scenarios. Try Them! Remember: AI Assistants make lots of mistakes Remember: AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini Without Proper Instructions

With Specific Instructions ChatGPT

ChatGPT Claude

Claude Perplexity

Perplexity Copilot

Copilot Gemini

Gemini Without Proper Instructions With Specific Instructions Without Proper Instructions Without Proper Instructions With Specific Instructions With Specific Instructions ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT Claude Claude Claude Claude Claude Claude Claude Claude Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Copilot Copilot Copilot Copilot Copilot Copilot Copilot Copilot Gemini Gemini Gemini Gemini Gemini Gemini Gemini Gemini Conclusion Always handle unknown cases cautiously. Defaults like "not found" can lead to severe security issues and financial losses. Make logging and denying unknown responses part of your development practices. Make shift-left decisions related to security while programming. Relations https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-viii-8mn3352 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-viii-8mn3352 Disclaimer Code Smells are my opinion . opinion Credits Photo by Nathana Rebouças on Unsplash Nathana Rebouças Unsplash https://www.youtube.com/watch?v=J2QOejhA6ek https://www.youtube.com/watch?v=J2QOejhA6ek Assumptions are the mother of all failures. Assumptions are the mother of all failures. Said Ouissal Said Ouissal Software Engineering Great Quotes Software Engineering Great Quotes This article is part of the CodeSmell Series. How to Find the Stinky Parts of your Code How to Find the Stinky Parts of your Code

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