Tags: web
Rating:
## Question
Are you good with numbers?
## Solution
Here we'd been given a webpage to submit 5 numbers, which had the source code like this-
```php
4 || !is_numeric($_POST['numbers'][$i])) {
continue;
}
$the_number = intval($_POST['numbers'][$i]);
if($the_number < 0) {
continue;
}
$numbers[] = $the_number;
}
$sum = intval(array_sum($numbers));
if($sum < 0) {
echo "You win a flag: $FLAG";
} else {
echo "You win nothing with number $sum ! :-(";
}
}
?>
```
```html
<html>
<head>
<title>Numberizer</title>
</head>
<body>
<h1>Numberizer</h1>
<form action="/" method="post">
<label for="numbers">Give me at most 10 numbers to sum!</label>
';
}
?>
<button type="submit">Submit</button>
</form>
To view the source code, click here.
</body>
</html>
```
Focus on the intval function, and by this logic, we'd have to somewhat do an overflow where the result is overall negative. So writing the first 4 numbers as `9e18` and the last number as `-9e18` and submit it, we get the flag: `ENO{INTVAL_IS_NOT_ALW4S_P0S1TiV3!}`
