Language: PHP
Label: safe
CWE: CWE-79 \u2014 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

Code:
    public function validateDirectiveAllowed($d)
    {
        if (is_null($d->allowed)) {
            return;
        }
        $this->with($d, 'allowed')
            ->assertNotEmpty()
            ->assertIsLookup(); // handled by InterchangeBuilder
        if (is_string($d->default) && !isset($d->allowed[$d->default])) {
            $this->error('default', 'must be an allowed value');
        }
        $this->context[] = 'allowed';
        foreach ($d->allowed as $val => $x) {
            if (!is_string($val)) {
                $this->error("value $val", 'must be a string');
            }
        }
        array_pop($this->context);
    }