The Meow Gallery plugin for WordPress is vulnerable to Stored Cross-Site Scripting via Attachment Alt Text (aria-label attribute) in all versions up to, and including, 5.5.1 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. The vulnerable code path is only reachable when a gallery item is rendered as a link (i.e., link_href is non-empty), and exploitation relies on the fact that WordPress's sanitize_text_field() strips angle-bracketed tags but preserves double quotes, allowing an attacker to break out of the aria-label attribute context and inject event-handler attributes such as onclick.
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