The Otter Blocks – Gutenberg Blocks, Page Builder for Gutenberg Editor & FSE PRO plugin for WordPress is vulnerable to Stored Cross-Site Scripting via file upload form, which allows SVG uploads, in all versions up to, and including, 2.6.3 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. Note that the patch in 2.6.4 allows SVG uploads but the uploaded SVG files are sanitized.