Information disclosure, also known as information leakage, is when a website unintentionally reveals sensitive information to its users.
Identify Information Disclosure
Fuzzing
If you identify interesting parameters, you can try submitting unexpected data types and specially crafted fuzz strings to see what effect this has. Pay close attention; although responses sometimes explicitly disclose interesting information, they can also hint at the application's behavior more subtly.
You can also use the Logger++ extension, available from the BApp store.