Resumen: A stored Cross-Site Scripting (XSS) vulnerability (CVE-2026-1903) affects the Ravelry Designs Widget plugin (version 1.0.0 and earlier). An authenticated user with Contributor privileges can store a malicious payload in the plugin’s sb_ravelry_designs shortcode layout attribute that may execute when the page is viewed. Below is a clear explanation, impact scenarios, detection steps, and remediation and hardening advice tailored for WordPress site owners.

TL;DR — The essentials

• Vulnerability: Stored XSS in Ravelry Designs Widget (<= 1.0.0).
• Attacker requirements: authenticated account with Contributor role or higher.
• Vector: sb_ravelry_designs shortcode layout attribute saved and later rendered without proper escaping.
• CVE: CVE-2026-1903
• CVSS v3.1 base score: 6.5 (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L)
• Immediate actions: deactivate or remove the plugin where possible; search for and remove malicious shortcode instances; restrict roles and review contributor accounts; rotate credentials if compromise suspected.
• Long-term: fix plugin code (sanitize & escape), enforce least privilege, and implement content-review workflows.

What happened — plain language explanation

The plugin exposes a shortcode named sb_ravelry_designs that accepts attributes including layout. In affected versions the layout attribute is not validated or escaped when saved and later rendered. A malicious contributor can craft a value containing JavaScript (or HTML event handlers) that gets stored in the database and executed in the browser of anyone who views the page where the shortcode appears.

Because the payload is persistent (stored), this is classified as stored XSS. Consequences range from session theft and unauthorized actions to content tampering, redirects, and delivery of secondary payloads depending on which accounts or visitors load the page.

Quién está en riesgo

• Sites running Ravelry Designs Widget plugin v1.0.0 or earlier.
• Sites allowing Contributor accounts (or higher) that are not fully trusted.
• Administrators, editors and other privileged users who preview or edit posts containing the vulnerable shortcode.
• Public visitors, if the payload targets anonymous users.

Note: The exploit requires an authenticated Contributor account to insert the payload; it is not an unauthenticated remote exploit.

Technical details (high-level, safe-for-publishing)

• Tipo de vulnerabilidad: Cross-Site Scripting almacenado (XSS)
• Vector: sb_ravelry_designs shortcode layout attribute saved and output without proper sanitization/escaping.
• Attack path: Contributor crafts attribute containing script/event handler or encoded JS; value saved to post content or options; when rendered in a browser the injected script executes.
• CVSS: 6.5 — reflects remote exposure via page view, low complexity, requires limited privileges, and user interaction (page view).

I will not publish exploit code. The guidance below focuses on detection, mitigation, and secure coding fixes.

Escenarios de explotación realistas

1. A contributor publishes a post containing the vulnerable shortcode with a malicious layout. When an editor previews the post in the admin area, their admin session may be exposed to the attacker’s script, enabling account takeover.
2. A contributor leaves the malicious shortcode in content that is later published publicly. Visitors load the page; the script runs and injects adverts, redirects, or loads additional scripts from attacker-controlled hosts.
3. A malicious contributor hides the payload or serves it conditionally so that only admins or editors see it during specific workflows (e.g., preview), targeting high-value accounts.

How to quickly identify if your site is affected

Prioritise detection across all WordPress installations you manage.

1. Inventory plugins and versions: Check all sites for Ravelry Designs Widget and confirm version. Any install at 1.0.0 or earlier is potentially vulnerable.
2. Search for occurrences of the shortcode in the database:

   Examples using WP-CLI:

   wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%sb_ravelry_designs%';"

   wp db query "SELECT option_name, option_value FROM wp_options WHERE option_value LIKE '%sb_ravelry_designs%';"

3. Escaneo automatizado: Use malware scanners or content scanners to search for sb_ravelry_designs combined with suspicious characters like <, >, javascript:, onerror, onload, eval.
4. Look for suspicious user activity: Check for recently added contributors or unusual email domains; audit recent posts and pending submissions.
5. Revisar registros: Review web and admin logs for POST requests to /wp-admin/post.php or /wp-admin/post-new.php from contributor accounts.

Immediate remediation steps (if you discover this plugin and can’t update yet)

If you find the plugin and an immediate vendor patch is not available, follow these emergency steps:

1. Desactive el plugin:

   Dashboard: Plugins → Installed Plugins → Deactivate. Or via WP-CLI:

   wp plugin deactivate ravelry-designs-widget

2. Search and clean injected shortcodes:

   Identify posts/pages/widgets with sb_ravelry_designs and inspect the layout attribute. Remove or sanitize suspicious instances.

   wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%sb_ravelry_designs%';"

   Backup before any bulk replace operations.

3. Lock down contributor accounts:

   Temporarily restrict ability to publish or require editorial review. Disable or quarantine suspicious contributor accounts.

4. Force password resets and rotate keys:

   Require admins and editors to reset passwords. Rotate API keys, OAuth tokens and other credentials if compromise is suspected.

5. Apply edge or application-level protections:

   If you run an edge WAF or application-layer protections, implement rules to block typical XSS payload markers in post submissions and editor POSTs.

6. Monitor logs and scan for persistence:

   Scan the filesystem for unknown PHP files, modified plugin/core files, and unexpected cron jobs. Review logs for suspicious activity.

7. Prepare to update or replace the plugin:

   Apply vendor patches as they become available. If the plugin is abandoned, remove it or replace it with a maintained alternative.

Short-term protection: rule guidance for WAF / edge filtering

If you can deploy rules at the edge or with an application firewall, block likely exploit patterns that combine the vulnerable shortcode with script or event handlers. Below are generic patterns — adapt and test to avoid false positives.

• Block POST submissions to editor endpoints that include sb_ravelry_designs plus substrings like <script, onerror=, onload=, javascript:, eval(, o equivalentes codificados.
• Block attribute values containing angle brackets or event-handler names, e.g. rules matching layout=".*(<|>|on\w+=|javascript:).*".
• Test rules in detect-only mode first, then escalate to blocking once tuned to reduce false positives.

How developers should fix the plugin (secure coding guidance)

Fixing the issue requires proper server-side validation and output escaping. Key principles:

1. Sanitizar al guardar: Restringir layout to a whitelist of allowed tokens (e.g., grid, list, carousel). Do not accept arbitrary HTML or JS.

   Example approach: check membership against $allowed = array('grid','list','carousel') and default to a safe value if not allowed.

2. Escapa en la salida: Uso esc_attr() for attribute contexts and esc_html() or wp_kses() with a strict allowlist for HTML output.

   Ejemplo: echo '<div class="ravelry-layout-'.esc_attr($layout).'">';

3. Nunca confíes en la entrada del usuario: Store validated tokens rather than raw user-supplied markup.
4. Use WordPress utilities: wp_kses(), sanitize_text_field(), esc_attr(), y esc_html().
5. Probar: Add unit tests and fuzzing for sanitization and rendering paths.

Detection and clean-up examples (practical steps)

1. Find suspicious posts:

   wp db query "SELECT ID, post_title, post_author FROM wp_posts WHERE post_content LIKE '%sb_ravelry_designs%';"

2. Review safely: Preview content using an isolated browser or a low-privilege account to avoid exposing high-value credentials.
3. Clean instances: Edit posts to remove or sanitise the layout attribute. Consider replacing vulnerable shortcodes with a safe placeholder.
4. Restaurar desde copias de seguridad limpias: If you find evidence of broader compromise (backdoors, new admin users), restore from a known-good backup after validation.
5. Auditoría de usuarios: List contributors and disable accounts that are suspicious:

   wp user list --role=contribuyente

6. Vuelve a escanear: After cleanup, re-run malware and file integrity scans to confirm no persistence remains.

Lista de verificación de respuesta a incidentes (paso a paso)

1. Contener: Deactivate the plugin and consider maintenance mode.
2. Investigar: Buscar en sb_ravelry_designs, review post revisions, and inspect logs for contributor activity.
3. Erradicar: Remove injected payloads, quarantine suspicious users, and remove unknown files or cron jobs.
4. Recuperar: Apply fixes or replace the plugin, change passwords, and rotate tokens.
5. Lecciones aprendidas: Determine how contributor access was granted and improve review and vetting processes.

Endurecimiento y prevención a largo plazo.

• Enforce the principle of least privilege — limit who can publish or insert shortcodes.
• Use content review workflows: contributors submit for review, editors approve.
• Limit free-form HTML and convert attributes to enumerated lists where possible.
• Run regular automated scans and file integrity checks.
• Choose actively maintained plugins with clear security practices.
• Keep WordPress core and plugins updated; test patches on staging when possible.
• Educate contributors not to paste untrusted HTML or shortcodes from external sources.

Sample search patterns / WP-CLI commands (safe to use)

• List posts with the shortcode:

  wp db query "SELECT ID, post_title FROM wp_posts WHERE post_content LIKE '%sb_ravelry_designs%';"

• Export suspected posts for offline analysis:

  wp post get <post_id> --field=post_content > suspicious_post_<id>.html

• List recent contributor users:

  wp user list --role=contributor --fields=ID,user_login,user_email,user_registered

Always take full backups before running bulk operations.

Why this matters — broader context

Stored XSS may appear less severe when the attacker starts with a low-privileged account, but it remains a common vector for escalation. Attackers can gain Contributor access through compromised signups or social engineering, then wait for admins or editors to preview content. Properly protecting the content pipeline (validation, review, and least privilege) is as important as securing the code.

Notas finales y pasos recomendados a seguir

1. Audit all sites for the Ravelry Designs Widget plugin and affected versions.
2. Deactivate or remove the plugin and/or remove vulnerable shortcodes until a patched version is available.
3. Buscar en la base de datos por sb_ravelry_designs and sanitize or remove suspicious entries.
4. Harden contributor workflows and restrict capabilities where feasible.
5. Deploy edge/application-level protections and content-scanning tools to block live exploitation attempts.
6. Update or fix plugin code to whitelist layout values and escape output when rendering.

If you need external help, seek an independent security consultant or a managed security provider without vendor bias. Prioritise containment and forensic review if you suspect compromise.