There is a lot of browser extensions developed by the community, here are my favorites.
All of this following extensions can be found in the HackerFox suite.
- Calomel SSL Validation : validate the grade of security of the SSL connection. The button will change color depending on the strength of encryption.
- HackBar : perfect to test SQL injections. Easy to use and some options like encoding (base64, url, hex), encryption (md5, sha-256, rot13). You can also alter POST data and your referer.
- HttpFox : display informations about the query : headers, cookies, POST data, time and so on…