What are the defect categories? With the knowledge of testing so far gained, you can now be able to categorize the defects you have found. Defects can be categorized into different types basing on the core issues they address. Some defects address security or database issues while others may refer to functionality or UI issues.Security Defects: Application security defects generally involve improper handling of data sent from the user to the application. These defects are the most severe and given highest priority for a fix.
Examples:
- Authentication: Accepting an invalid username/password
- Authorization: Accessibility to pages though permission not given

Data Quality/Database Defects: Deals with improper handling of data in the database.
Examples:
- Values not deleted/inserted into the database properly
- Improper/wrong/null values inserted in place of the actual values

Critical Functionality Defects: The occurrence of these bugs hampers the crucial functionality of the application.
Examples:- Exceptions

Functionality Defects: These defects affect the functionality of the application.
Examples:
- All Javascript errors
- Buttons like Save, Delete, Cancel not performing their intended functions
- A missing functionality (or) a feature not functioning the way it is intended to
- Continuous execution of loops

User Interface Defects: As the name suggests, the bugs deal with problems related to UI are usually considered less severe.
Examples:
- Improper error/warning/UI messages
- Spelling mistakes
- Alignment problems