Background: Due to a now-fixed ambiguity in the documentation for the
remove_query_arg() functions, many plugins were using them incorrectly, allowing for potential XSS attack vectors in their code.
remove_query_arg() have an optional argument to define the base query string to use. If this argument is undefined, it will use
$_SERVER['REQUEST_URI'], which is unescaped. When printed out to a page, this could be used as an XSS attack vector.
The easiest way to fix this in your plugin A plugin is a piece of software containing a group of functions that can be added to a WordPress website. They can extend functionality or add new features to your WordPress websites. WordPress plugins are written in the PHP programming language and integrate seamlessly with WordPress. These can be free in the WordPress.org Plugin Directory https://wordpress.org/plugins/ or can be cost-based plugin from a third-party is to escape the output of
remove_query_arg(). When it’s being printed to a page (for example as a link), you should use
esc_url(). When it’s being used in HTTP HTTP is an acronym for Hyper Text Transfer Protocol. HTTP is the underlying protocol used by the World Wide Web and this protocol defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. headers or as part of a HTTP request (for example, as part of a location redirect header The header of your site is typically the first thing people will experience. The masthead or header art located across the top of your page is part of the look and feel of your website. It can influence a visitor’s opinion about your content and you/ your organization’s brand. It may also look different on different screen sizes. or in a
wp_remote_get() call), you should use
Edit by Ipstenu: Also read Sucuri’s reasonable disclosure on the matter. Many plugins have been patched and auto-updated in a massive coordinated effort to stem this one before it gets nasty.