Bug report: URL DECODE MISS "+"

var%20strKey1%20%3D%20%22JaVa3C41ptIsAGo0DStAff%22%3B%0Avar%20strKey2%20%3D%20%22CaNUknOWThIsK3y%22%3B%0Avar%20strKey3%20%3D%20String.fromCharCode%2871%2C%2048%2C%20111%2C%20100%2C%2033%29%3B%0Aif%20%28uname%20%3D%3D%20%28strKey3%20+%20%28%28%28strKey1.toLowerCase%28%29%29.substring%280%2C%20strKey1.indexOf%28%220%22%29%29%20+%20strKey2.substring%282%2C%206%29%29.toUpperCase%28%29%29.substring%280%2C%2015%29%29%29%20%7B%0A%20%20%20%20var%20strKey4%20%3D%20%27Java_Scr1pt_Pa4sW0rd_K3y_H3re%27%3B%0A%20%20%20%20if%20%28upass%20%3D%3D%20%28strKey4.substring%28strKey4.indexOf%28%271%27%2C%205%29%2C%20strKey4.length%20-%20strKey4.indexOf%28%27_%27%29%20+%205%29%29%29%20%7B%0A%20%20%20%20%20%20%20%20alert%28%27Login%20Success%21%27%29%3B%0A%20%20%20%20%20%20%20%20document.getElementById%28%27key%27%29.innerHTML%20%3D%20unescape%28%22%253Cfont%2520color%253D%2522%2523000%2522%253Ea2V5X0NoM2NrXy50eHQ%3D%253C/font%253E%22%29%3B%0A%20%20%20%20%7D%20else%20%7B%0A%20%20%20%20%20%20%20%20alert%28%27Password%20Error%21%27%29%3B%0A%20%20%20%20%7D%0A%7D%20else%20%7B%0A%20%20%20%20alert%28%27Login%20Failed%21%27%29%3B%0A%7D

var strKey1 = "JaVa3C41ptIsAGo0DStAff";
var strKey2 = "CaNUknOWThIsK3y";
var strKey3 = String.fromCharCode(71, 48, 111, 100, 33);
if (uname == (strKey3 (((strKey1.toLowerCase()).substring(0, strKey1.indexOf("0")) strKey2.substring(2, 6)).toUpperCase()).substring(0, 15))) {
var strKey4 = 'Java_Scr1pt_Pa4sW0rd_K3y_H3re';
if (upass == (strKey4.substring(strKey4.indexOf('1', 5), strKey4.length - strKey4.indexOf('_') 5))) {
alert('Login Success!');
document.getElementById('key').innerHTML = unescape("%3Cfont%20color%3D%22%23000%22%3Ea2V5X0NoM2NrXy50eHQ=%3C/font%3E");
} else {
alert('Password Error!');
}
} else {
alert('Login Failed!');
}

Reproduce the report in CyberChef's URL Decode operation using the supplied input and compare how the plus sign is handled. Done means URL decoding preserves or converts the plus sign according to the operation's intended behavior, with a regression check covering this case.

Written by the indexing model from the issue text.