Multiple plugins for WordPress are vulnerable to Stored Cross-Site Scripting via the plugin's bundled FancyBox JavaScript library (versions 1.3.4 to 3.5.7) in various versions due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

The Freemius SDK, as used by hundreds of WordPress plugin and theme developers, was vulnerable to Cross-Site Request Forgery and Information disclosure due to missing capability checks and nonce protection on the _get_debug_log, _get_db_option, and the _set_db_option functions in versions up to, and including 2.4.2. Any WordPress plugin or theme running a version of Freemius less than 2.4.3 is vulnerable.

Numerous Plugins and Themes from the AccessPress Themes (aka Access Keys) vendor are backdoored due to their website being compromised. Only plugins and themes downloaded via the vendor website are affected, and those hosted on wordpress.org are not. However, all of them were updated or removed to avoid any confusion

The Easy Contact Form Pro WordPress plugin before 1.1.1.9 did not properly sanitise the text fields (such as Email Subject, Email Recipient, etc) when creating or editing a form, leading to an authenticated (author+) stored cross-site scripting issue. This could allow medium privilege accounts (such as author and editor) to perform XSS attacks against high privilege ones like administrator.