ahilles107 / web-publisher

Preventing Cross-Site-Scripting Attacks

Cross-Site-Scripting allows an attacker to inject malicious code into your website - in particular Javascript code, and have that code executed with the privileges of a visiting user. This can be used to obtain data, or perform actions on behalf of that visiting user.

In order to prevent this, make sure to escape all user-provided data:

// for HTML
$sanitized = htmlentities($tainted, ENT_QUOTES);

// for URLs
$sanitized = urlencode($tainted);

General Strategies to prevent injection

In general, it is advisable to prevent any user-data to reach this point. This can be done by white-listing certain values:

if ( ! in_array($value, array('this-is-allowed', 'and-this-too'), true)) {
    throw new \InvalidArgumentException('This input is not allowed.');
}

For numeric data, we recommend to explicitly cast the data:

$sanitized = (integer) $tainted;

This check looks for parameters that are defined as one type in their type hint or doc comment but seem to be used as a narrower type, i.e an implementation of an interface or a subclass.

Consider changing the type of the parameter or doing an instanceof check before assuming your parameter is of the expected type.

Preventing Cross-Site-Scripting Attacks

Cross-Site-Scripting allows an attacker to inject malicious code into your website - in particular Javascript code, and have that code executed with the privileges of a visiting user. This can be used to obtain data, or perform actions on behalf of that visiting user.

In order to prevent this, make sure to escape all user-provided data:

// for HTML
$sanitized = htmlentities($tainted, ENT_QUOTES);

// for URLs
$sanitized = urlencode($tainted);

General Strategies to prevent injection

In general, it is advisable to prevent any user-data to reach this point. This can be done by white-listing certain values:

if ( ! in_array($value, array('this-is-allowed', 'and-this-too'), true)) {
    throw new \InvalidArgumentException('This input is not allowed.');
}

For numeric data, we recommend to explicitly cast the data:

$sanitized = (integer) $tainted;

It seems like the type of the argument is not accepted by the function/method which you are calling.

In some cases, in particular if PHP’s automatic type-juggling kicks in this might be fine. In other cases, however this might be a bug.

We suggest to add an explicit type cast like in the following example:

function acceptsInteger($int) { }

$x = '123'; // string "123"

// Instead of
acceptsInteger($x);

// we recommend to use
acceptsInteger((integer) $x);