URL Redirection to Untrusted Site ('Open Redirect') vulnerability in the HTML5 scrubber in rrrene html_sanitize_ex allows an unauthenticated remote attacker to retarget a form already on the rendering page and receive whatever the victim submits, including credentials, via the form and formaction attributes on an <input> element in sanitized HTML. HTML's form attribute associates an input with any form on the page by its id even when the input sits outside that form, and formaction on a submit control overrides the owning form's action. Neither attribute receives a scheme check, so an absolute cross-origin URL survives sanitizing.

No script executes. The scrubber allows neither form nor button, so the attacker cannot introduce a form of their own and the rendering page must already contain a form carrying an id.

This issue affects html_sanitize_ex: from 0.3.1 before 1.5.3.

AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:H/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CWE-601

https://cna.erlef.org/cves/CVE-2026-66370.html

https://github.com/rrrene/html_sanitize_ex/commit/a1e804ed997e780ea71d14393cf2f701330553a6

https://github.com/rrrene/html_sanitize_ex/security/advisories/GHSA-w3f9-jjhw-wwvq

https://osv.dev/vulnerability/EEF-CVE-2026-66370

[{"vendor":"rrrene","product":"html_sanitize_ex","defaultStatus":"unaffected","collectionURL":"https://repo.hex.pm","packageName":"html_sanitize_ex","cpes":["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"],"modules":["Elixir.HtmlSanitizeEx.Scrubber.HTML5","Elixir.HtmlSanitizeEx"],"programFiles":["lib/html_sanitize_ex/scrubber/html5.ex","lib/html_sanitize_ex.ex"],"programRoutines":[{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':scrub_attribute/2"},{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':sanitize/1"},{"name":"'Elixir.HtmlSanitizeEx':html5/1"}],"repo":"https://github.com/rrrene/html_sanitize_ex","packageURL":"pkg:hex/html_sanitize_ex","versions":[{"version":"0.3.1","lessThan":"1.5.3","versionType":"semver","status":"affected"}]},{"vendor":"rrrene","product":"html_sanitize_ex","defaultStatus":"unaffected","collectionURL":"https://github.com","packageName":"rrrene/html_sanitize_ex","cpes":["cpe:2.3:a:rrrene:html_sanitize_ex:*:*:*:*:*:*:*:*"],"modules":["Elixir.HtmlSanitizeEx.Scrubber.HTML5","Elixir.HtmlSanitizeEx"],"programFiles":["lib/html_sanitize_ex/scrubber/html5.ex","lib/html_sanitize_ex.ex"],"programRoutines":[{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':scrub_attribute/2"},{"name":"'Elixir.HtmlSanitizeEx.Scrubber.HTML5':sanitize/1"},{"name":"'Elixir.HtmlSanitizeEx':html5/1"}],"repo":"https://github.com/rrrene/html_sanitize_ex","packageURL":"pkg:github/rrrene/html_sanitize_ex","versions":[{"version":"8976d64ea0b77d26093a94a43ec48a3978e8d028","lessThan":"a1e804ed997e780ea71d14393cf2f701330553a6","versionType":"git","status":"affected"}]}]