hello sabhajeet, in this case you'd have to reset your master password - please refer to the following article: Reset your Primary Password if you've forgotten it

The Master Password is only used for accessing names and passwords that are stored in the Password Manager. If you have a problem with cookies then you need to look elsewhere.

Details like websites remembering you (log you in automatically) are stored in a cookie.

• Create a cookie 'allow' exception to keep such cookies, especially in case of secure websites and when cookies expire when Firefox is closed.
• Tools > Options > Privacy > "Use custom settings for history" > Cookies: Exceptions

• http://kb.mozillazine.org/Cookies
• https://support.mozilla.org/kb/Deleting+cookies

Separate Issue; Update your Flash Player v16.0.0.287
https://www.adobe.com/products/flashplayer/distribution3.html

In the event that the passwords information is lost, you should record all information in a separate text file somewhere else on your hard drive, or written down. You can easily copy and paste if you need to do so. If you are concerned about someone else looking at that file, you can compress it using a password.