CVE-2026-0751: Deep Dive — Authenticated (Author) Stored XSS in Payment Page Plugin

Update (13 Feb 2026): A stored Cross‑Site Scripting (XSS) vulnerability affecting the Payment Page (Payment Form for Stripe) WordPress plugin (versions ≤ 1.4.6) has been disclosed. The flaw permits an authenticated user with Author privileges to save content via the parameter pricing_plan_select_text_font_family that is later rendered to visitors without sufficient sanitization or escaping. Below is a technical analysis, impact assessment, detection guidance, and practical mitigations written in the concise, pragmatic tone I use when advising Hong Kong site owners and security teams.

Executive summary

• Software: Payment Page (Payment Form for Stripe) WordPress plugin
• Vulnerable versions: ≤ 1.4.6
• Vulnerability: Stored Cross‑Site Scripting (XSS) via pricing_plan_select_text_font_family
• CVE: CVE‑2026‑0751
• Required privilege: Author (authenticated)
• CVSS (reported): ~5.9 (Medium) — requires authenticated Author and some user interaction
• Reported by: Athiwat Tiprasaharn (Jitlada) — published 13 Feb 2026

Summary: an authenticated Author can supply a malicious value intended for a font parameter that the plugin stores and later outputs to site visitors without proper validation/escaping. The stored nature means many visitors can be affected; consequences range from UI tampering and phishing to session theft depending on the site context.

Why this matters: stored XSS in a payment UI

Payment and pricing interfaces are high‑trust areas on web sites. Stored XSS in those components is especially dangerous because:

• JavaScript executes in the site’s origin — attackers may access cookies, perform actions as users, or intercept form inputs if same‑origin policies permit.
• Injected UI can mislead visitors (phishing or fraudulent prompts) and cause financial or reputational harm.
• Stored payloads persist and affect every visitor who views the infected page, amplifying impact.

In Hong Kong and other jurisdictions with active eCommerce and payment activity, the reputational and regulatory consequences make prompt mitigation essential.

Technical summary of the flaw

• Entry point: parameter pricing_plan_select_text_font_family, intended for font selection or label text.
• Weakness: plugin accepts and stores input, later rendering it in HTML without context‑aware escaping or strict validation.
• Attack vector: authenticated user (Author role or higher) injects malicious content via the plugin UI or settings. When visitors load the page, the stored content is rendered and executed.
• Outcome: stored XSS — arbitrary JavaScript execution in visitors’ browsers.

The root cause appears to be lack of validation/whitelisting for values expected to be plain font names and failure to escape at output. A secure approach would whitelist fonts and ensure all stored values are rendered as plain text or safely escaped.

Who’s at risk?

• Sites running Payment Page (Payment Form for Stripe) plugin versions ≤ 1.4.6.
• Sites that grant Authors (or equivalent roles) the ability to edit pricing settings or plugin UI.
• Multi‑author blogs, membership sites, editorial platforms, and any site where third parties can modify displayed content.

If Authors are tightly controlled and fully vetted, immediate risk is lower; if accounts are shared, reused, or managed by external contractors, risk increases.

Exploitability and impact assessment

Exploitability: Medium — attacker needs an authenticated Author account. No unauthenticated remote exploit is indicated.

Impact: Variable. Possible outcomes include:

• Low–medium: UI tampering, redirects, nuisance scripts.
• High: session theft, credential harvesting, capture of payment or personal data when forms share origin, or distribution of malicious payloads.

Because the vulnerability is stored, a single injection may compromise many visitors over time.

Practical detection: indicators you can check now

1. Inventory: Confirm plugin presence and version via WordPress admin (Plugins > Installed Plugins). Identify pages that display pricing plan UI.
2. Audit user roles: List accounts with Author privileges or higher and review recent changes to pricing or plugin settings.
3. Search stored data: Query database tables (e.g., wp_postmeta, plugin options) for suspicious strings containing HTML tags (<script>, onerror, etc.) or encoded variants.
4. Page inspection: Visit public pages that render pricing plans, view source, and inspect for unescaped values containing HTML/JS.
5. Logs: Examine server access logs and admin activity logs (if available) for unexpected POSTs to plugin endpoints.

If you find stored HTML or JavaScript in fields intended for plain font names, treat that as evidence of exploitation or misconfiguration.

Immediate mitigation steps (for site owners)

The following actions are prioritised for speed and safety:

1. Reduce exposure
   • Temporarily restrict Author and Contributor privileges. Downgrade untrusted Authors to Contributor or Subscriber while investigating.
   • If feasible, disable public display of pricing pages until remediation is complete.
2. Virtual patching / WAF rules
   • Deploy WAF rules to block attempts to submit HTML/script/event attributes to parameters that should be plain text. Ensure POST bodies and common encodings are inspected.
   • If you do not operate your own WAF, ask your host or security team to apply targeted rules for the parameter in question.
3. Harden output and rendering
   • If you can edit plugin templates or use a theme override, escape user-controlled values with WordPress APIs: esc_html(), esc_attr(), or wp_kses() as appropriate.
   • For font names, validate against a whitelist and reject values containing suspicious characters or tokens (e.g., <, >, onerror, javascript:).
4. Update or remove the plugin
   • Check for an official plugin update that fixes the issue. If none is available, consider removing or replacing the plugin temporarily.
5. Audit and clean stored payloads
   • Search and sanitize plugin-stored values in a staging environment before re‑importing to production.
   • When in doubt, remove suspect entries and restore clean content from backups.
6. Notify stakeholders
   • Inform site administrators, security contacts, and any third‑party authors about the incident and steps taken.

For developers: secure coding and how this should be fixed

Fixes should address input validation, storage rules, escaping on output, and capability checks:

1. Input validation
   • Whitelist allowed font names (letters, numbers, hyphen, comma, space) or a fixed set of supported fonts.
   • Reject or sanitize any input containing markup tokens (<, >, ;, javascript:, event handler names).
2. Output escaping
   • Escape values at the point of output using context‑appropriate functions: esc_attr() for attributes, esc_html() for body content, esc_js() for JS contexts.
   • Avoid inserting user-controlled data into inline JavaScript or unescaped CSS strings where possible.
3. Storage rules
   • Store canonical, safe values instead of arbitrary markup. Use tokens or references for selectable values.
4. Capability checks and nonces
   • Verify server-side capabilities (e.g., current_user_can()) and use WordPress nonces for form submissions.
5. Testing
   • Add unit/integration tests and security regression tests that check sanitization for all user inputs.

What a responsible disclosure and patch lifecycle looks like

1. Triage: validate and reproduce the issue in a controlled environment.
2. Scope: identify affected versions and code paths.
3. Fix: implement validation and escaping, prepare a patch.
4. Release: publish a patched plugin update and advisory with coordinated disclosure.
5. Mitigation: publish WAF signatures or rules to reduce exposure while updates are staged.
6. Communication: notify users and hosts with clear mitigation steps.

Defensive controls and virtual patching (vendor‑neutral guidance)

While awaiting a plugin patch, layered controls reduce risk. Key defensive measures include:

• WAF / Virtual patching: Apply targeted rules to block submission of script tags, event handlers, and suspicious encoded payloads to the parameter(s) in question. Ensure the WAF inspects POST bodies and common encodings.
• Content scanning: Periodically scan stored content for injected HTML/JS and alert administrators on detection.
• Role‑aware policies: Add extra scrutiny or approval for requests originating from Author accounts when changing plugin settings.
• Monitoring & alerts: Monitor blocked attempts and administrative changes to detect attempts to exploit the vulnerability.

Recommended WAF rule strategy (high level)

• Block or sanitize parameters expected to contain font-family values when they include:
• < or > characters
• Tokens such as script, javascript:, data:, vbscript:
• Event handler patterns like on\w+ (e.g., onerror)
• Encoded equivalents (e.g., <, %3C)
• Rate‑limit requests that update plugin settings, particularly from Author accounts.
• Require administrative reapproval for changes that introduce new inline content or custom HTML.
• On page render, detect and alert on responses that contain user-supplied HTML where plain text is expected.

Incident response checklist (if you find an injection)

1. Contain
   • Disable the affected page(s) or put them in maintenance mode.
   • Disable the vulnerable plugin if feasible.
2. Clean
   • Remove malicious stored values from the database. Work in staging before touching production.
   • Revoke sessions and force logout for users if you suspect credential exposure.
3. Recover
   • Apply a plugin patch, replace the plugin, or restore clean backups.
4. Review
   • Conduct a post‑incident audit for backdoors, modified files, or scheduled tasks.
   • Rotate credentials or keys that may have been exposed.
5. Report and learn
   • Document the incident, remediation steps, and improvements to workflows and code review practices.

Long‑term hardening recommendations

• Apply least privilege for user roles; prefer a contributor-review workflow where possible.
• Use a centralized, well-tested input validation/sanitization library for plugins and custom code.
• Deploy a Content Security Policy (CSP) to reduce the impact of XSS by limiting script sources and disallowing inline scripts where feasible.
• Set cookies with HttpOnly and appropriate SameSite attributes.
• Regularly scan plugins and themes with static and dynamic tools for known vulnerabilities.
• Test plugin updates in staging and use code review for third‑party plugin changes.
• Maintain automated backups and test restores periodically.

What to do if you can’t immediately patch the plugin

• Apply WAF rules to block suspicious inputs to the parameter(s) in question.
• Limit Authors’ ability to update pricing plans; require administrative review for changes.
• Disable public pages rendering the affected content where possible.
• Sanitize existing stored values in the database to remove markup.
• Plan a controlled plugin replacement or update rather than leaving a vulnerable plugin installed long term.

Example safe sanitization approach (developer guidance)

Below is a high‑level approach illustrating validation and escaping. This is guidance — not an exploit.

<?php
$allowed_fonts = array( 'Arial', 'Helvetica', 'Times New Roman', 'Georgia', 'Courier New' );
$font_input = isset( $_POST['pricing_plan_select_text_font_family'] ) ? sanitize_text_field( wp_unslash( $_POST['pricing_plan_select_text_font_family'] ) ) : '';

if ( in_array( $font_input, $allowed_fonts, true ) ) {
    // Safe to store the canonical name
    update_option( 'pp_font_family', $font_input );
} else {
    // Reject or log unexpected input
    wp_die( 'Invalid font selection.' );
}
?>

Escape on output:

<?php
$font = get_option( 'pp_font_family', 'Arial' );
$font_attr = esc_attr( $font ); // safe for HTML attribute
echo '<div class="pricing" style="font-family: ' . $font_attr . ';">' . esc_html( $pricing_label ) . '</div>';
?>

If freeform HTML must be supported, use wp_kses() with a strictly constrained allowed list and avoid inserting user data into JavaScript or unescaped attributes.

Communication guidance for site owners

• Prioritise high‑exposure sites first: eCommerce, high traffic, membership platforms, or any site processing payments.
• Inform internal teams and external contractors about role restrictions and recent plugin changes.
• Keep a timeline of actions (containment, remediation, notification) for incident records and potential regulatory needs.

Final thoughts

Stored XSS in widely used plugins is a persistent threat. This vulnerability reinforces two key lessons:

1. Plugin and theme authors must enforce strict input validation and context‑aware escaping, particularly for fields exposed to non‑technical editors.
2. Layered defenses — role hardening, virtual patching/WAFs, monitoring, and secure development practices — significantly reduce the window of exposure.

If your site uses the Payment Page (Payment Form for Stripe) plugin at versions ≤ 1.4.6, act promptly: restrict untrusted Author privileges, apply WAF rules to block HTML/JavaScript in font fields, sanitize stored content, and update or replace the plugin when a safe version is available.

Author: Hong Kong security expert

Published: 13 Feb 2026