The Blocksy Companion plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 2.1.46 via the saveattachments function. This is due to the Custom Fonts extension registering a wpcheckfiletypeandext filter that approves any filename containing .woff2 or .ttf as a substring via strpos() rather than validating that those strings appear as the final extension via PATHINFOEXTENSION — allowing double-extension filenames such as shell.woff2.php to pass MIME validation and be handled as permitted font files. This makes it possible for unauthenticated attackers to upload files that may be executable, which makes remote code execution possible. This vulnerability is only exploitable when the premium version of the plugin (blocksy-companion-pro) is installed with both the WooCommerce Extra (Advanced Reviews) and Custom Fonts extensions active; the free blocksy-companion plugin does not contain the vulnerable code paths.

Blocksy Companion Pro plugin for WordPress before 2.1.47 contains an unauthenticated arbitrary file upload vulnerability that allows attackers to upload executable files by bypassing extension validation in the saveattachments function exposed through the Advanced Reviews feature. Attackers can exploit the Custom Fonts extension's flawed strpos() substring check by uploading double-extension filenames such as shell.woff2.php, causing the validation to pass on the substring match while the web server executes the file as PHP, achieving remote code execution.

The Blocksy Companion plugin for WordPress is vulnerable to authenticated arbitrary file upload in all versions up to, and including, 2.1.19. This is due to insufficient file type validation detecting SVG files, allowing double extension files to bypass sanitization while being accepted as a valid SVG file. This makes it possible for authenticated attackers, with author level access and above, to upload arbitrary files on the affected site's server which may make remote code execution possible.

The Blocksy theme for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's blocks in all versions up to, and including, 2.0.26 due to insufficient input sanitization and output escaping on user supplied attributes like 'className' and 'radius'. This makes it possible for authenticated attackers with contributor-level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

The Blocksy Companion plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's Newsletter widget in all versions up to, and including, 2.0.31 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers with contributor-level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

The Blocksy theme for WordPress is vulnerable to Stored Cross-Site Scripting via the className parameter in the About Me block in all versions up to, and including, 2.0.39 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

The Blocksy theme for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘tagName’ parameter in versions up to, and including, 2.0.42 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

The Blocksy Companion plugin for WordPress is vulnerable to Stored Cross-Site Scripting via SVG uploads in versions up to, and including, 2.0.45 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

The Blocksy theme for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘hasfieldlinkrel’ parameter in all versions up to, and including, 2.0.46 due to insufficient input sanitization and output escaping. 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 Blocksy theme for WordPress is vulnerable to Stored Cross-Site Scripting via the Contact Info Block link parameter in all versions up to, and including, 2.0.77 due to insufficient input sanitization and output escaping. 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 Blocksy Companion plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's blocksynewslettersubscribe shortcode in all versions up to, and including, 2.1.10 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 Blocksy Companion plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the plugin's 'blocksynewslettersubscribe' shortcode in all versions up to, and including, 2.1.14 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 Blocksy Companion plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'tagName' Block Attribute (blocksy/dynamic-data) in all versions up to, and including, 2.1.51 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with author-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.