Reflected XSS in AshAuthentication confirmation and magic link interaction forms

{
  "id": "e853e05b68f3d166737e4b5ebb727d9f703f91b6b5cf9ed37807f7e9b04498fe",
  "url": "https://osv.dev/vulnerability/CVE-2026-66882",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Reflected XSS in AshAuthentication confirmation and magic link interaction forms",
    "summary": "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",
    "evidence": "osv:CVE-2026-66882",
    "products": [],
    "severity": "low",
    "structured": {
      "id": "CVE-2026-66882",
      "aliases": [
        "CVE-2026-66882",
        "EEF-CVE-2026-66882",
        "GHSA-54fc-x3hv-ffhw"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/team-alembic/ash_authentication",
              "type": "GIT",
              "events": [
                {
                  "introduced": "fe0b4558dbe852fee5d81a460a8355577618a8c8"
                },
                {
                  "fixed": "62719710790a150a9eacab9c0a066e0d122d15be"
                },
                {
                  "introduced": "cf2095dda5d489ee37166cfce0905f6bd21f4761"
                },
                {
                  "fixed": "5a32a74e99d38b58d5b7e94c986c96356d5cd3e3"
                },
                {
                  "introduced": "6767fe27eb952e5bc09aa2e5a7d8f96f5a1c424a"
                },
                {
                  "fixed": "d1dc61ad0e5034ee3d41dce6cf83eea94dcd46d3"
                },
                {
                  "fixed": "0bd5199db066be22b2ca1ec8bc6109e5d62e6070"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "fe0b4558dbe852fee5d81a460a8355577618a8c8"
                      },
                      {
                        "fixed": "62719710790a150a9eacab9c0a066e0d122d15be"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "ChangesAt"
                  },
                  {
                    "range": [
                      {
                        "introduced": "4.8.0"
                      },
                      {
                        "fixed": "4.14.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "5.0.0-rc.0"
                      },
                      {
                        "fixed": "5.0.0-rc.13"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "fixed": "62719710790a150a9eacab9c0a066e0d122d15be"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0bd5199db066be22b2ca1ec8bc6109e5d62e6070"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v4.14.1",
            "v5.0.0-rc.12",
            "v5.0.0-rc.11",
            "v5.0.0-rc.10",
            "v4.14.0",
            "v4.13.7",
            "5.0.0-rc.9",
            "5.0.0-rc.8",
            "v5.0.0-rc.7",
            "v5.0.0-rc.6",
            "v5.0.0-rc.5",
            "v5.0.0-rc.4",
            "v5.0.0-rc.3",
            "v5.0.0-rc.2",
            "v5.0.0-rc.1",
            "v5.0.0-rc.0",
            "v4.13.6",
            "v4.13.5",
            "v4.13.4",
            "v4.13.3",
            "v4.13.2",
            "v4.13.1",
            "v4.13.0",
            "v4.12.0",
            "v4.11.0",
            "v4.10.0",
            "v4.9.9",
            "v4.9.8",
            "v4.9.7",
            "v4.9.6",
            "v4.9.5",
            "v4.9.4",
            "v4.9.3",
            "v4.9.2",
            "v4.9.1",
            "v4.9.0",
            "v4.8.7",
            "v4.8.5",
            "v4.8.4",
            "v4.8.3",
            "v4.8.2",
            "v4.8.1",
            "v4.8.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-66882.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:29.813023746Z",
      "provider": "osv",
      "references": [
        "https://cna.erlef.org/cves/CVE-2026-66882.html",
        "https://github.com",
        "https://osv.dev/vulnerability/EEF-CVE-2026-66882",
        "https://repo.hex.pm",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66882.json",
        "https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-54fc-x3hv-ffhw",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-66882",
        "https://github.com/team-alembic/ash_authentication/commit/0bd5199db066be22b2ca1ec8bc6109e5d62e6070",
        "https://github.com/team-alembic/ash_authentication/commit/62719710790a150a9eacab9c0a066e0d122d15be",
        "https://github.com/team-alembic/ash_authentication"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-79"
        ],
        "cna_assigner": "EEF",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66882.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-66882",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496710,
  "published_at": "2026-08-25T08:03:47.721+00:00"
}