{"id":"GHSA-5crx-pfhq-4hgg","aliases":["CVE-2026-34974"],"title":"phpMyFAQ: SVG Sanitizer Bypass via HTML Entity Encoding Leads to Stored XSS and Privilege Escalation","description":"### Summary\nThe regex-based SVG sanitizer in phpMyFAQ (`SvgSanitizer.php`) can be bypassed using HTML entity encoding in `javascript:` URLs within SVG `` attributes. Any user with `edit_faq` permission can upload a malicious SVG that executes arbitrary JavaScript when viewed, enabling privilege escalation from editor to full admin takeover.\n\n### Details\nThe file `phpmyfaq/src/phpMyFAQ/Helper/SvgSanitizer.php` (introduced 2026-01-15) uses regex patterns to detect dangerous content in uploaded SVG files. The regex for `javascript:` URL detection is:\n\n`/href\\s*=\\s*[\"\\']javascript:[^\"\\']*[\"\\']/i`\n\nThis pattern matches the literal string `javascript:` but fails when the URL is HTML entity encoded. For example, `javascript:` decodes to `javascript:` in the browser, but does NOT match the regex. The `isSafe()` method returns `true`, so the SVG is accepted without sanitization.\n\nAdditionally, the `DANGEROUS_ELEMENTS` blocklist misses ``, ``, and `` elements which can also be used to execute JavaScript in SVG context.\n\nUploaded SVG files are served with `Content-Type: image/svg+xml` and no `Content-Disposition: attachment` header, so browsers render them inline and execute any JavaScript they contain.\n\nThe image upload endpoint (`/admin/api/content/images`) only requires the `edit_faq` permission — not full admin — so any editor-level user can upload malicious SVGs.\n\n### PoC\n### Basic XSS (confirmed working in Chrome 146 and Edge)\n\n1. Login to phpMyFAQ admin panel with any account that has `edit_faq` permission\n2. Navigate to Admin → Content → Add New FAQ\n3. In the TinyMCE editor, click the image upload button\n4. Upload this SVG file:\n\n```xml\n\n\n \n Click for XSS\n \n\n```\n\n5. The SVG is uploaded to `/content/user/images/_.svg`\n6. Open the SVG URL directly in a browser\n7. Click the red text → `alert(document.domain)` executes\n\n### Privilege Escalation (Editor → Admin Takeover)\n\n1. As editor, upload this SVG:\n\n```xml\n\n\n \n 📋 System Notice\n r.json()).then(d=>document.title='pwned')\">\n \n View Update →\n \n\n```\n\n2. Send the SVG URL to an admin\n3. Admin opens URL, clicks \"View Update →\"\n4. JavaScript creates backdoor admin user `backdoor:H4ck3d!`\n5. Attacker logs in as `backdoor` with full admin privileges\n\n\n### Impact\nThis is a Stored Cross-Site Scripting (XSS) vulnerability that enables privilege escalation. Any user with `edit_faq` permission (editor role) can upload a weaponized SVG file. When an admin views the SVG, arbitrary JavaScript executes in their browser on the phpMyFAQ origin, allowing the attacker to:\n- Create backdoor admin accounts via the admin API\n- Exfiltrate phpMyFAQ configuration (database credentials, API tokens)\n- Modify or delete FAQ content\n- Achieve full admin account takeover\nThe vulnerability affects all phpMyFAQ installations using the `SvgSanitizer` class (introduced 2026-01-15). Recommended fix: replace regex-based sanitization with a DOM-based allowlist approach, or serve SVG files with `Content-Disposition: attachment` to prevent inline rendering.","severity":"medium","score":5.4,"published":"2026-04-01T23:42:47.000Z","modified":"2026-04-06T17:34:13.869Z","withdrawn":false,"knownExploited":false,"affected":[{"ecosystem":"Packagist","name":"thorsten/phpmyfaq","ranges":[{"events":[{"introduced":"0"},{"fixed":"4.1.1"}],"type":"ECOSYSTEM"}],"versions":["2.10.0-alpha","2.8.0","2.8.0-RC","2.8.0-RC2","2.8.0-RC3","2.8.0-RC4","2.8.0-alpha2","2.8.0-alpha3","2.8.0-beta","2.8.0-beta2","2.8.0-beta3","2.8.1","2.8.10","2.8.11","2.8.12","2.8.13","2.8.14","2.8.15","2.8.16","2.8.17","2.8.18","2.8.19","2.8.2","2.8.20","2.8.21","2.8.22","2.8.23","2.8.24","2.8.25","2.8.26","2.8.27","2.8.28","2.8.29","2.8.3","2.8.4","2.8.5","2.8.6","2.8.7","2.8.8","2.8.9","2.9.0","2.9.0-alpha","2.9.0-alpha2","2.9.0-alpha3","2.9.0-alpha4","2.9.0-beta","2.9.0-beta2","2.9.0-rc","2.9.0-rc2","2.9.0-rc3","2.9.0-rc4","2.9.1","2.9.10","2.9.11","2.9.12","2.9.13","2.9.2","2.9.3","2.9.4","2.9.5","2.9.6","2.9.7","2.9.8","2.9.9","3.0.0","3.0.0-RC","3.0.0-RC.2","3.0.0-alpha","3.0.0-alpha.2","3.0.0-alpha.3","3.0.0-alpha.4","3.0.0-beta","3.0.0-beta.2","3.0.0-beta.3","3.0.1","3.0.10","3.0.11","3.0.12","3.0.2","3.0.3","3.0.4","3.0.5","3.0.6","3.0.7","3.0.8","3.0.9","3.1.0","3.1.0-RC","3.1.0-alpha","3.1.0-alpha.2","3.1.0-alpha.3","3.1.0-beta","3.1.1","3.1.10","3.1.11","3.1.12","3.1.13","3.1.14","3.1.15","3.1.16","3.1.17","3.1.18","3.1.2","3.1.3","3.1.4","3.1.5","3.1.6","3.1.7","3.1.8","3.1.9","3.2.0","3.2.0-RC","3.2.0-RC.2","3.2.0-RC.4","3.2.0-alpha","3.2.0-beta","3.2.0-beta.2","3.2.1","3.2.10","3.2.2","3.2.3","3.2.4","3.2.5","3.2.6","3.2.7","3.2.8","3.2.9","4.0.0","4.0.0-RC","4.0.0-RC.2","4.0.0-RC.3","4.0.0-RC.4","4.0.0-RC.5","4.0.0-alpha","4.0.0-alpha.2","4.0.0-alpha.3","4.0.0-alpha.4","4.0.0-beta","4.0.0-beta.2","4.0.1","4.0.10","4.0.11","4.0.12","4.0.13","4.0.14","4.0.15","4.0.16","4.0.18","4.0.19","4.0.2","4.0.3","4.0.4","4.0.5","4.0.6","4.0.7","4.0.8","4.0.9","4.1.0","4.1.0-RC","4.1.0-RC.2","4.1.0-RC.4","4.1.0-RC.5","4.1.0-RC.6","4.1.0-RC.7","4.1.0-alpha","4.1.0-alpha.2","4.1.0-alpha.3","4.1.0-beta","4.1.0-beta.2"],"fixed":["4.1.1"]}],"references":["https://github.com/thorsten/phpMyFAQ/security/advisories/GHSA-5crx-pfhq-4hgg","https://nvd.nist.gov/vuln/detail/CVE-2026-34974","https://github.com/thorsten/phpMyFAQ","https://github.com/thorsten/phpMyFAQ/releases/tag/4.1.1"],"sources":[{"name":"OSV","id":"GHSA-5crx-pfhq-4hgg","modified":"2026-04-06T17:34:13.869869Z","url":"https://osv.dev/vulnerability/GHSA-5crx-pfhq-4hgg"}],"assessments":[{"source":"OSV","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","score":5.4}]}