CVE-2026-76839

Grav prior to 3.8.5 in the Login plugin twofa_cancel task accepts a client-controlled _redirect field without a nonce and allows an unauthenticated request to set an external http, https, or protocol-relative Location target. Controller::execute() applies the field when taskTwofa_cancel() sets no redirect, and Grav::getRedirectResponse() accepts the target through Uri::isExternal(), enabling phishing redirects from a trusted Grav host.

Grav before 2.0.14 contains a stored cross-site scripting vulnerability in the Security::detectXss() function (system/src/Grav/Common/Security.php). All XSS detection patterns use the PCRE /u (UTF-8) modifier, so a single invalid UTF-8 byte anywhere in page content causes preg_match() to return false for every pattern, silently bypassing the save-time XSS safety gate (Validation::checkSafety()). An authenticated attacker with page-edit permissions (without the security.xss_whitelist privilege) can store malicious JavaScript that executes in the browser of a visitor who views the affected page.

Grav before 2.0.15 contains a stored cross-site scripting vulnerability in the audio and video media rendering through the sourceParsedownElement method. The media URL fragment is concatenated unescaped into rawHtml source elements, allowing attackers to inject arbitrary HTML and JavaScript that executes in viewers' sessions.

Grav before version 2.0.15 contains a stored cross-site scripting vulnerability in the detectXss() function where unpaired quotes in unquoted attribute values bypass event-handler detection. Authenticated editors can inject event handlers like onerror= that pass validation and execute in visitor browsers when page content is rendered.

Grav before 2.0.15 contains a path traversal vulnerability in the static asset server within index.php that uses string prefix matching instead of directory-boundary validation. Unauthenticated attackers can access files in sibling directories by exploiting directory names that extend the base path string, such as requesting assets-secret when assets is the configured base.

Grav versions from 1.5.2 through 2.0.12 contain a stored cross-site scripting vulnerability in the Security::detectXss() function (system/src/Grav/Common/Security.php). The event-handler scan is anchored at `<` and uses `[^>]*?`, which cannot cross the first literal `>`; when a `>` appears inside a quoted attribute value the browser keeps the tag open and parses a subsequent event handler (e.g. onerror), so the detector and browser disagree. A page editor without admin.super privileges can save page content such as `<img src=x title=">" onerror=alert(document.domain)>`, which is accepted, stored, and executed in the site origin when any visitor (including unauthenticated users) views the page. Fixed in 2.0.13.

Grav before version 2.0.1 contains a decompression bomb vulnerability in the ZipArchiver::extract() method, which lacks limits on uncompressed size, file count, and nesting depth. Attackers can supply a crafted ZIP archive that expands to fill available disk space, causing denial of service by exhausting storage resources.

Grav before version 2.0.2 contains a Twig sandbox bypass that allows a page author (any admin.pages user, or anyone able to write to user/pages) to exfiltrate configuration secrets. Although the sandbox replaces the 'config' variable with a redacted facade and strips Config::get/toArray from the method allowlist, the raw container remains accessible via the allow-listed grav.offsetGet('config'), which returns the real Config object. Allow-listed object-dumping filters (json_encode, print_r, yaml_encode) then serialize that object at the PHP level without invoking the sandbox method gate, exposing the full config tree including plugin secrets such as SMTP credentials, API keys, and plugin DB credentials.

Grav before version 2.0.0 (up to 2.0.0-rc.9 and the 2.0 branch) contains a stored CSS injection vulnerability in the Markdown image resize() media action. Prior media hardening rejects direct ?style= payloads and unsafe attribute() fallbacks, but the resize() action in Excerpts::processMediaActions() writes caller-controlled values directly into the image's styleAttributes. A lower-privileged content editor who can edit page Markdown can store a crafted image URL with semicolon-delimited CSS declarations in the resize parameters, which are rendered into the final <img style=...> attribute when a higher-privileged reviewer/admin views the page or preview.

Grav before version 2.0.0-beta.2 contains an XML external entity injection (XXE) vulnerability in SVG file upload processing that allows authenticated attackers to read arbitrary files. The application uses simplexml_load_string without disabling external entity loading, enabling attackers to inject XXE payloads via malicious SVG files.