Easy Image Collage <= 1.13.6 - Authenticated (Author+) Stored Cross-Site Scripting via 'grid[properties][borderColor]' and 'grid[images][N][attachment_url]' Parameters

The Easy Image Collage plugin for WordPress is vulnerable to Stored Cross-Site Scripting via 'grid[properties][borderColor]' and 'grid[images][N][attachment_url]' Parameters in all versions up to, and including, 1.13.6 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. Because the data is stored via update_post_meta() rather than wp_insert_post() post content, WordPress's unfiltered_html restriction does not apply, meaning Authors cannot be blocked from this attack path by capability controls alone.