Sanitizing CSS attributes using safecss_filter_attr in WordPress
The safecss_filter_attr function in WordPress is responsible for filtering and sanitizing CSS styles within HTML attributes. The function is designed to ensure that only safe and valid CSS is included within these attributes, which can help to prevent potential security vulnerabilities associated with malicious CSS.
The function operates by parsing the CSS styles within an HTML attribute, examining each individual style declaration. It checks whether each declaration is considered safe according to a predefined list of safe CSS properties and values.
If a style declaration is deemed safe, it is included in the final output. If it is not, it is excluded. This filtering and sanitization process helps to ensure that the resulting HTML attributes contain only safe and valid CSS.
It is worth noting that the safecss_filter_attr function does not modify the original CSS styles. Instead, it returns a new string that contains only the safe style declarations. This ensures that the original data remains intact and unmodified, while still providing a mechanism for ensuring the safety and validity of the CSS.
Parameters of the safecss_filter_attr Function in WordPress
The safecss_filter_attr function in WordPress accepts two parameters which are detailed below:
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$css(string, required): This refers to a string that contains CSS rules. -
$deprecated(string, optional, default value: ”): This parameter is not utilized.
Return Value of the safecss_filter_attr Function
The safecss_filter_attr function returns a string that is the filtered version of the CSS rules string that was passed to it.
Examples
How to use safecss_filter_attr function to filter CSS rules
$css = 'color: blue; font-size: 16px;';
$filtered_css = safecss_filter_attr($css);
echo $filtered_css;
In the above example, the safecss_filter_attr function is used to filter a string of CSS rules. The CSS rules are passed as a string to the function. The function returns the filtered CSS rules.
How to use safecss_filter_attr function to filter CSS rules with invalid properties
$css = 'color: blue; font-size: 16px; invalid-property: value;';
$filtered_css = safecss_filter_attr($css);
echo $filtered_css;
In this example, the safecss_filter_attr function is used to filter a string of CSS rules that contain an invalid property. The function will remove any invalid properties from the CSS rules, and return the filtered CSS rules.
How to use safecss_filter_attr function to filter CSS rules and apply them to an HTML element
$css = 'color: blue; font-size: 16px;';
$filtered_css = safecss_filter_attr($css);
echo '<div style="' . esc_attr($filtered_css) . '">This is a div with filtered CSS rules.</div>';
In this example, the safecss_filter_attr function is used to filter a string of CSS rules, and then the filtered CSS rules are applied to a HTML div element. The function esc_attr is used to escape the filtered CSS rules to ensure they are safe to be used in the HTML code.
Conclusion
The safecss_filter_attr function in WordPress serves as a crucial tool for ensuring the safety and integrity of the CSS attributes within your website. It functions by filtering and sanitizing the CSS within inline styles. By doing so, it helps prevent malicious or harmful code from being executed on your site. This function is particularly useful in scenarios where user-inputted CSS needs to be sanitized, such as in custom themes or plugins, thereby maintaining the security of your WordPress site.