Browser Lock Pro by Darshan Parmar

Browser Lock Pro protects your browsing session with a master password.

Features:
- Lock instantly with the toolbar button or Alt+L (Alt+Shift+L on Mac)
- Optional lock on browser startup and when all windows are closed and reopened
- Optional auto-lock after your computer is idle (set in Settings)
- New tabs and windows are blocked while locked
- Your open tabs are restored exactly as they were when you unlock
- Change your master password from the lock screen or from Settings
- Dark, high-contrast lock screen
- Brute-force protection: 15-second cooldown after 5 wrong attempts

Privacy: Your password is never stored. Only a salted PBKDF2 (SHA-256) hash is kept, locally in the browser. The extension does not collect or send any data, and does not touch your cookies, history or Firefox Account data.

Note: this is a convenience lock to keep casual snoops out of your open session. It does not encrypt your profile on disk, and Firefox's own Safe Mode or other profiles are outside its control.