Input validation vulnerability in ActivityPub 0.17.0

The ActivityPub plugin for WordPress is vulnerable to a type of attack called Stored Cross-Site Scripting in versions 0.17.0 and earlier. This attack allows attackers with contributor-level or higher permissions to inject malicious web scripts into pages that are accessed by other users. When someone visits a page that has been injected with malicious scripts, the scripts run and can cause harm to the user. To protect against this vulnerability, users should update to the latest version of the ActivityPub plugin, which has improved input sanitization and output escaping.