team-alembic ash_authentication up to 4.14.1/5.0.0-rc.12 Confirmation Form confirmation_form.html.eex confirm cross site scripting

Summaryinfo

A vulnerability was found in team-alembic ash_authentication up to 4.14.1/5.0.0-rc.12. It has been declared as problematic. Impacted is the function AshAuthentication.AddOn.Confirmation.Plug.accept/AshAuthentication.Strategy.MagicLink.Plug.accept of the file lib/ash_authentication/add_ons/confirmation/confirmation_form.html.eex of the component Confirmation Form. Executing a manipulation of the argument confirm can lead to cross site scripting. This vulnerability is registered as CVE-2026-66882. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability has been found in team-alembic ash_authentication up to 4.14.1/5.0.0-rc.12 and classified as problematic. This vulnerability affects the function AshAuthentication.AddOn.Confirmation.Plug.accept/AshAuthentication.Strategy.MagicLink.Plug.accept of the file lib/ash_authentication/add_ons/confirmation/confirmation_form.html.eex of the component Confirmation Form. The manipulation of the argument confirm with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. CVE summarizes:

Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in team-alembic AshAuthentication allows reflected cross-site scripting via the confirmation and magic link interaction forms. When a strategy is configured with require_interaction? set to true, AshAuthentication serves an intermediate HTML page asking the user to confirm the action by submitting a form. Both such pages embed a request parameter directly into a hidden input's value attribute without HTML escaping: lib/ash_authentication/add_ons/confirmation/confirmation_form.html.eex interpolates the confirm parameter, and lib/ash_authentication/strategies/magic_link/sign_in_form.html.eex interpolates the magic link token parameter. These templates are compiled with EEx.function_from_file/3 using plain <%= %> expressions, which perform no escaping, so the parameter is reflected verbatim. Neither accept handler validates the value before rendering it. AshAuthentication.AddOn.Confirmation.Plug.accept/2 only checks that a confirm key is present, and AshAuthentication.Strategy.MagicLink.Plug.accept/2 reads the parameter directly, so no token signature is verified at this stage and arbitrary attacker-supplied text reaches the template. An unauthenticated attacker can therefore craft a URL whose parameter terminates the attribute and injects markup, for example a quote followed by a <script> element. Because the accept phase is served over GET, loading the crafted link is sufficient; no form submission or prior authentication is required. The injected script executes in the origin of the application embedding AshAuthentication, giving it access to that origin's cookies, session, and same-origin responses. Since these pages are part of the authentication flow, a victim following what appears to be a legitimate confirmation or sign-in link is a plausible target. This issue affects ash_authentication: from 4.8.0 before 4.14.2 and from 5.0.0-rc.0 before 5.0.0-rc.13.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-66882 since 07/28/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 4.14.2 or 5.0.0-rc.13 eliminates this vulnerability.

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Productinfo

Vendor

• team-alembic

Name

• ash_authentication

Version

• 4.14.0
• 4.14.1
• 5.0.0-rc.0
• 5.0.0-rc.1
• 5.0.0-rc.2
• 5.0.0-rc.3
• 5.0.0-rc.4
• 5.0.0-rc.5
• 5.0.0-rc.6
• 5.0.0-rc.7
• 5.0.0-rc.8
• 5.0.0-rc.9
• 5.0.0-rc.10
• 5.0.0-rc.11
• 5.0.0-rc.12

Website

• Product: https://github.com/team-alembic/ash_authentication/

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