Remediation & cleanup if you find malicious payloads

1. Take the site to maintenance mode if practical.
2. Backup the site and database (snapshot for forensics).
3. Remove malicious content from posts and postmeta; restore safe revisions.
4. Rotate admin passwords, API keys and other secrets.
5. Invalidate sessions and require password resets for admins/editors.
6. Scan files for webshells and unauthorized changes (focus on wp-content/uploads, themes, plugins).
7. Remove unknown scheduled tasks, suspicious users and options.
8. If credentials were exfiltrated, escalate to full incident response and forensic analysis.
9. After cleanup, reinstall WordPress core, themes and plugins from trusted sources.

If you are unsure how to proceed, engage a professional security incident responder.

Developer guidance — secure shortcode patterns and fixes

If you maintain or develop the plugin, fix the shortcode handler and apply robust sanitization and escaping.

Key principles:

• Never echo user input directly.
• Validate inputs strictly (e.g., stock tickers should be alphanumeric and short).
• Sanitize input on save and escape on output.
• Use wp_kses with a strict allowlist if HTML output is required.
• Restrict who can submit HTML (capability checks) and use nonces for requests.

Illustrative safe shortcode handler (example):

function is_valid_stock_symbol( $symbol ) {
    // Accept uppercase letters, numbers, hyphen; max length 10
    return preg_match( '/^[A-Z0-9\-]{1,10}$/', $symbol );
}

function safe_stock_shortcode_handler( $atts ) {
    $atts = shortcode_atts( array(
        'symbol' => '',
        'show'   => 'price',
    ), $atts, 'stock' );

    // sanitize attributes
    $symbol = strtoupper( sanitize_text_field( $atts['symbol'] ) );
    if ( ! is_valid_stock_symbol( $symbol ) ) {
        return '';
    }

    $show = sanitize_text_field( $atts['show'] );
    $allowed_show = array( 'price', 'change', 'name' );
    if ( ! in_array( $show, $allowed_show, true ) ) {
        $show = 'price';
    }

    $symbol_escaped = esc_html( $symbol );
    $show_escaped   = esc_attr( $show );

    $output  = '';
    $output .= '' . $symbol_escaped . '';
    $output .= '';

    return $output;
}
add_shortcode( 'stock', 'safe_stock_shortcode_handler' );

Notes:

• Validate symbols; reject unexpected input.
• Use sanitize_text_field and escaping functions (esc_html, esc_attr).
• Only allow raw inner HTML for users with appropriate capabilities and sanitise with wp_kses using a strict allowlist.
• Do not store untrusted HTML or scripts in postmeta or options.

Example hardening changes at plugin level

• Add capability checks so raw HTML is only accepted by users with unfiltered_html capability.
• Escape on output: esc_html() for text nodes, esc_attr() for attributes.
• Sanitize before storing and escape again on output — defence in depth.
• Use nonces for AJAX and form endpoints and validate capabilities in REST/AJAX handlers.

WAF / virtual patching perspective (general guidance)

When a plugin fix is not yet available, virtual patching via a WAF or hosting-level rules can reduce risk. Goals for rules:

• Block attempts to save shortcodes containing script tags or inline event handlers.
• Block admin/post requests with common XSS signatures in POST bodies.
• Optionally, neutralise or strip script tags from POST payloads before WordPress saves them (use with caution).
• Prevent stored XSS payloads that reference sensitive APIs (e.g., document.cookie, XMLHttpRequest) from being saved.

Operational advice:

• Tune rules to reduce false positives; some legitimate content may contain code samples.
• Prefer challenge (captcha) in sensitive situations where false positives are likely, rather than outright block.
• Log all blocked attempts and investigate the sources of blocked traffic.

Suggested WAF regex examples (illustrative)

Test these on a staging environment before deploying to production.

• Block POST requests where a [stock shortcode contains script tags or suspicious patterns:

  (?i)\[stock[^\]]*(|on\w+\s*=|javascript:|data:text/html)

• Block inline event handlers:

  (?i)on(?:click|mouseover|load|error|submit)\s*=

• Block javascript: URIs:

  (?i)javascript\s*:

Adjust rules to your environment to avoid breaking legitimate content.

Longer‑term hardening checklist

• Least privilege: grant Contributor/editor roles only when necessary; consider custom roles with stricter capabilities.
• Editorial workflow: require review and limit who can preview or publish shortcode-containing content.
• Disable dangerous shortcodes for untrusted roles.
• Ensure unfiltered_html is not granted to non-trusted roles.
• Apply a strict Content Security Policy (CSP) to reduce impact of inline scripts (not a replacement for proper sanitization).
• Maintain an inventory of installed plugins/themes and remove unused ones.
• Regular backups and tested restore procedures.
• Role-based testing: simulate Contributor workflows to identify unsafe rendering paths.
• Monitor server and WAF logs for anomalies and blocked XSS attempts.

Incident response playbook (brief)

1. Contain: Deactivate plugin, disable shortcodes, take site offline if needed.
2. Triage: Identify injected posts/metadata, collect logs and preserve evidence.
3. Clean: Remove payloads, unknown admin users and altered files.
4. Recover: Restore from a clean backup or reinstall components from trusted sources.
5. Post‑mortem: Identify root cause, patch and update processes to avoid recurrence.
6. Notify: If user data was exposed, follow legal and disclosure obligations.

How to detect vulnerable shortcodes in the database (quick SQL)

Search for posts containing the shortcode and possible script tags:

SELECT ID, post_title
FROM wp_posts
WHERE post_content LIKE '%[stock%'
AND post_content LIKE '%

SELECT post_id, meta_key, meta_value
FROM wp_postmeta
WHERE meta_value LIKE '%[stock%'
OR meta_value LIKE '%

wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%[stock%' AND post_content LIKE '%

// Neutralize 'stock' shortcode: return safe placeholder and log the incident
if ( shortcode_exists( 'stock' ) ) {
    remove_shortcode( 'stock' );
    add_shortcode( 'stock', function( $atts ) {
        error_log( 'Blocked stock shortcode rendering in ' . (is_admin() ? 'WP-admin' : 'Front-end') );
        return '';
    } );
}