All About OWASP #3 - Sensitive Data Exposure

As part of secure programming under SOUND Programming Methodology, we will explore the third security threat, Sensitive Data Exposure. We have already covered:

What is Sensitive Data Exposure?

This occurs when our application doesn’t protect the users' sensitive data. These below items can be classified as Sensitive Data:

  • Credit card number
  • SSN, DOB or any personal information
  • Bank Account and Routing number
  • Any identification Number
  • Credentials to access any system
  • Health Information

Scenario and preventions for Sensitive Data Exposure

Scenario #1 - Transmission over an unsecured channel
  • Transmitting data in clear text without HTTPS is a big risk.
  • Use valid SSL certificate and keep certificate active.
  • Some web pages are not over HTTPS and intruders may get access to the website from these unsecured pages.


  • Always use HTTPS for communication.
  • Transmitted data should be encrypted with secure protocol TLS with PFS (Perfect Forward Secrecy)
  • Enforce encryption using directives like HSTS (HTTPS Strict Transport Security)

Scenario #2 - Unsecured Storage

  • Storage of credentials and other sensitive data should be very secure.
  • Sensitive data is NOT stored securely.
  • Archive of sensitive data is not maintained under the same strict security measures.


  • Store passwords using strong adaptive and salted hashing functions with a work factor (delay factor), such as Argon2, scrypt, bcrypt, or PBKDF2.
  • Even after retrieval, sensitive data should NOT be passed through the unsecured channel.

Scenario #3 - Weak Encryption and old algorithms

  • Use of old or default encryption techniques.
  • Use of unsalted password or simple hashes.


  • User proper key management for encryption and apply rotation policy on them.
  • Don’t use obsolete and default encryption mechanism for secure sensitive data.
  • Hashes generated by simple or fast hash functions may be cracked by GPUs, even if they were salted, so this should be taken care of.
  • Ensure to encrypt stored data at rest.

Scenario #4 - Saving of unnecessary data

  • Non-adherence with EU's General Data Protection Regulation (GDPR), or regulations.
  • Not complying with PCI DSS (Data Security Standard) and other govt regulations


  • Data which is not saved, can’t be stolen.
  • Disable caching for sensitive data at any stage.

Scenario #5 – Insufficient control and improper classification of data

  • Data access with insufficient privilege may lead to a big security threat.


  • Data should be classified correctly.
  • Access to records should be properly configured and should be given access based on that only.

With this introduction, I hope you got a very good overview of OWASP Threat #3, Sensitive Data Exposure, and will take care in your code and code review. It may NOT be applicable to all applications but is recommended to consider with Banking and Finance, Healthcare and Insurance related applications. 

Originally published at taagung

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