Important: test these rules on staging. Some legitimate advanced content may trip rules. Start with detection-only, then tighten.

Hardening recommendations (site owners and admins)

• Principle of least privilege: review and limit Contributor roles. Require Editors to review/publish where practical.
• Strict content review: enforce manual publishing or moderation workflows.
• Keep plugins and themes updated; apply security patches within 48–72 hours when severity dictates.
• Enforce 2FA for all Editor/Administrator accounts.
• Use strong password policies and rotate REST API/application passwords.
• Restrict access to the block editor if not required for certain roles.
• Enable a conservative Content Security Policy (CSP) that disallows inline scripts and only permits trusted hosts — this reduces the practical impact of many XSS vectors.
• Set secure cookie flags (HttpOnly, Secure, SameSite) for authentication cookies.

Developer guidance: fix the root cause

If you maintain plugins or work with the Info Cards codebase, apply the following secure-coding practices to eliminate this class of vulnerability:

1. Sanitize inputs server-side on save
   • Do not rely only on client-side validation.
   • For textual attributes, use sanitize_text_field() or wp_strip_all_tags().
   • For allowed HTML, use wp_kses() with a strict allowlist.
   • For JSON attributes, parse and validate each field explicitly; do not persist raw serialized HTML from untrusted users.
2. Escape outputs when rendering
   • Escape attributes with esc_attr(); escape content with esc_html() or wp_kses_post(), as appropriate.
   • When printing block attributes into HTML attributes, use esc_attr() or json_encode() to ensure safety.
3. Use register_block_type() render callbacks safely
   • If using server-side render_callback, sanitize and escape everything before returning markup.
   • Avoid echoing user content directly; compose strings using safe escaping functions.
4. Do not trust Gutenberg editor behavior
   • Block attribute values can be manipulated via the editor or crafted REST requests. Validate on save and on render.
5. Capability-aware UI
   • Expose rich editors only to trusted roles; provide simplified, strictly sanitized fields for Contributor-level users.
6. Logging and monitoring
   • Log suspicious content patterns and rate-limit content saves from low-privileged users.

Post-incident checklist (if you find malicious content)

1. Isolate and patch: update or deactivate the plugin.
2. Quarantine suspicious posts: set status to draft until reviewed.
3. Scan the site (files and database) for injected scripts and backdoors:
   • Check uploads, mu-plugins, active theme files, and wp-content for unexpected files.
   • Inspect cron jobs and admin-ajax usage for unusual tasks.
4. Rotate credentials:
   • Reset passwords for admin/editor accounts.
   • Revoke and recreate API keys and application passwords.
5. Audit user accounts:
   • Remove suspicious users or those created near the incident time.
   • Check for unauthorized privilege changes.
6. Re-run vulnerability and malware scans; correlate findings with WAF logs.
7. Notify stakeholders and follow legal/privacy obligations if data exposure is suspected.
8. If tampering is deep and cannot be reliably cleaned, restore from a known-good backup and reapply safe updates.

Monitoring & detection: ongoing

• Implement file integrity monitoring to detect unauthorized changes.
• Log content save events with editor IPs and payload summaries to detect anomalous patterns.
• Keep WAF rules updated; automate deployments where possible.
• Monitor plugin vulnerability disclosures and subscribe to security alerts.
• Run regular automated scans of post_content and postmeta for suspicious markup.

Final notes for site owners (Hong Kong perspective)

Do not underestimate the risk posed by low-privilege accounts: Contributors can be converted into persistence mechanisms through stored XSS. Prioritise patching to 2.0.8 (or disabling the plugin until you can update). Combine patching with access control, WAF rules, CSP, and monitoring to close the window of opportunity for attackers.

If you are uncomfortable making these changes yourself, consult an experienced WordPress security professional or your internal security team for assistance.

Action now: review Contributor accounts and verify the Info Cards plugin version immediately. Patch to 2.0.8 or deactivate the plugin until you can — this removes the immediate attack vector.