Quick and dirty code to decode your LastPass vault.
Get your vault by using the technique Wladimir Palant provided, and supplied in the Security Now! Show notes at https://www.grc.com/sn/SN-904-Notes.pdf
fetch("https://lastpass.com/getaccts.php", {method: "POST"})
.then(response => response.text())
.then(text => console.log(text.replace(/>/g, ">\n")));
Then run this powershell to get a text output of your accounts in the vault and any decodeable values.
It's really quick and dirty right now, I'm working on making it cleaner.
.\Decode-LPVault.ps1 | Out-File LPVault.txt
You can get the result as an object
$vaultObj = .\Decode-LPVault.ps1 -objOut
$vaultObj.VaultAsString is the text that was output by the original version
$vaultObj.accounts.account.URLDecoded will show you all the URLs in your vault associated with logins.