To properly secure sensitive data storage in Salesforce applications, follow these best practices: 1. **Use Protected Custom Settings or Metadata**: Store sensitive data like API keys, passwords, and cryptographic keys in protected custom settings or metadata fields. 2. **Encrypt Data**: Encrypt sensitive data before storing it in custom objects, and keep the encryption key in a protected custom setting or metadata field. 3. **Avoid Public Storage**: Do not store sensitive data in public custom settings, metadata, or unencrypted fields. 4. **Use Salesforce Cryptography APIs**: Leverage Salesforce's Apex Crypto APIs for encryption and decryption instead of custom cryptography. 5. **Set Proper Permissions**: Restrict access to fields containing encrypted data to authorized users only. 6. **Avoid Logging Sensitive Data**: Do not log sensitive information like secrets or credentials in debug logs or production environments. 7. **Secure Client Applications**: Use secure storage mechanisms like keychains or password managers for client-side applications, avoiding direct storage in browser-based apps. 8. **Follow Least Privilege Principle**: Grant users only the permissions they need to perform their tasks. These steps will help you mitigate risks and ensure secure handling of sensitive data.