diff --git a/helpers.lua b/helpers.lua
index d490857..6ddf7b5 100644
--- a/helpers.lua
+++ b/helpers.lua
@@ -1019,14 +1019,6 @@ function login()
     -- Forward the `r` URI argument if it exists to redirect
     -- the user properly after a successful login.
     if uri_args.r then
-        -- If `uri_args.r` contains line break, someone is probably trying to
-        -- pass some additional headers
-        if string.match(uri_args.r, "(.*)\n") then
-            flash("fail", t("redirection_error_invalid_url"))
-            logger.debug("Redirection url is invalid")
-            return redirect(conf.portal_url)
-        end
-
         return redirect(conf.portal_url.."?r="..uri_args.r)
     else
         return redirect(conf.portal_url)
@@ -1065,6 +1057,25 @@ end
 -- Set cookie and redirect (needed to properly set cookie)
 function redirect(url)
     logger.debug("Redirecting to "..url)
+    -- For security reason we don't allow to redirect onto unknown domain
+    -- And if `uri_args.r` contains line break, someone is probably trying to
+    -- pass some additional headers
+
+    -- This should cover the following cases:
+    -- https://malicious.domain.tld/foo/bar
+    -- http://malicious.domain.tld/foo/bar
+    -- https://malicious.domain.tld:1234/foo
+    -- malicious.domain.tld/foo/bar
+    -- (/foo/bar, in which case no need to make sure it's prefixed with https://)
+    if not string.starts(url, "/") and not string.starts(url, "http://") and not string.starts(url, "https://") then
+        url = "https://"..url
+    end
+    local domain = url:match("^https?://([%w%.]*)/?")
+    if string.match(url, "(.*)\n") or (domain ~= nil and not is_in_table(conf["domains"], domain)) then
+        logger.debug("Unauthorized redirection to "..url)
+        flash("fail", t("redirection_error_invalid_url"))
+        url = conf.portal_url
+    end
     return ngx.redirect(url)
 end