You forgot your password? With this account, or do you have another account to which you have lost access? If the account for which you have forgotten the password is this one, which might be a better option since the account is still logged in on your device, that simply means that there is every possibility that the account login details are saved and remembered in your browser.

If that's the case, try going through your browser's saved passwords and checking to see if your forum password is among your saved details there.

Note: Saving login details is also not really advisable because your information can be compromised when your email linked to the browser is hacked.