diff --git a/docs/services/routing.md b/docs/services/routing.md
index 9eb275e..d749cfa 100644
--- a/docs/services/routing.md
+++ b/docs/services/routing.md
@@ -229,6 +229,12 @@ This fragment belongs in `config/http.yaml`. List the frontend's exact origin; `
 The rules surf applies to the origin answer:
 
 - `supports_credentials: true` together with `*` in `allowed_origins` fails the start-up. A credentialed answer that trusted any origin would let every site read responses made with the user's cookies; Laravel's php-cors reflects the origin in that case, surf refuses it.
+- With `supports_credentials: true`, three more rules close other spellings of the same exposure, and each refusal names the key with its index, such as `http.cors.allowed_origins[1]`:
+  - an `allowed_origins` entry with a `*` is accepted only when the scheme is literal and the `*` is the whole leftmost host label, as in `https://*.example.com`; `https://*`, `*://*`, `https://*example.com` and `http*://www.example.com` fail the start-up;
+  - every `allowed_origins_patterns` entry must be anchored with `^` and `$`, as in `^https://[a-z]+\.example\.com$`; an unanchored pattern matches inside any origin, so `https://.*\.example\.com` would trust `https://x.example.com.attacker.net`;
+  - no origin rule may match an origin outside the configured domains: surf tries each rule against probe origins such as `https://cors-probe.invalid` and `null`, which refuses `https://*.com` and `^https?://.*$`.
+
+  Without credentials these entries load as before.
 - An allowed origin is echoed exactly in `Access-Control-Allow-Origin`; `*` is sent only for `allowed_origins: ["*"]` without credentials, and that answer is unchanged from earlier releases.
 - When the answer depends on the request's `Origin` (with `supports_credentials`, with any pattern, or with more than one listed origin), every response on a CORS path carries `Vary: Origin`, the preflight and a disallowed origin's response included, so a shared cache never serves one origin's answer to another.
 - An `allowed_origins` entry with a `*` inside, such as `https://*.example.com`, matches like Laravel's `Str::is`: the `*` stands for any characters and the rest is literal.
diff --git a/modules/surf/README.md b/modules/surf/README.md
index 17bf773..d9019fa 100644
--- a/modules/surf/README.md
+++ b/modules/surf/README.md
@@ -154,8 +154,8 @@ The generated application `main` wires surf in with `surf.ServeCommand` and `sur
 | `http.body_limits.upload_bytes` | none, required | Upload body cap in bytes. Must be a whole number of at least 1; it is validated at boot. |
 | `http.trusted_proxies` | empty | List of CIDRs whose `X-Forwarded-For` header is trusted when resolving the client IP. Malformed entries are skipped. |
 | `http.cors.paths` | empty | Path globs (`api/*`) that get CORS headers. With no `http.cors` section no CORS headers are sent. |
-| `http.cors.allowed_origins` | empty | Allowed origins, echoed exactly; `*` allows any (without credentials only). An entry with a `*` inside, such as `https://*.example.com`, matches any characters there, as Laravel's `Str::is` does. |
-| `http.cors.allowed_origins_patterns` | empty | Go regular expressions matched against the origin. A pattern that does not compile, or one still wrapped in PHP delimiters (`#^...$#`), fails boot. |
+| `http.cors.allowed_origins` | empty | Allowed origins, echoed exactly; `*` allows any (without credentials only). An entry with a `*` inside, such as `https://*.example.com`, matches any characters there, as Laravel's `Str::is` does. With credentials, such a `*` must be the whole leftmost host label after a literal scheme (`https://*.example.com`; `https://*` and `*://*` fail boot), and no entry may match an origin outside the configured domains. |
+| `http.cors.allowed_origins_patterns` | empty | Go regular expressions matched against the origin. A pattern that does not compile, or one still wrapped in PHP delimiters (`#^...$#`), fails boot. With credentials, a pattern must be anchored with `^` and `$` and must not match an origin outside the configured domains (`^https?://.*$` fails boot). |
 | `http.cors.allowed_methods` | empty | Methods sent in `Access-Control-Allow-Methods`; `*` allows any. |
 | `http.cors.allowed_headers` | empty | Headers sent in `Access-Control-Allow-Headers`; `*` allows any. |
 | `http.cors.exposed_headers` | empty | Headers sent in `Access-Control-Expose-Headers`. |
diff --git a/modules/surf/cors.go b/modules/surf/cors.go
index 0d0dde3..659d422 100644
--- a/modules/surf/cors.go
+++ b/modules/surf/cors.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net/http"
 	"regexp"
+	"regexp/syntax"
 	"strconv"
 	"strings"
 
@@ -25,7 +26,10 @@ type CORSConfig struct {
 // LoadCORSConfig reads http.cors. Missing section yields a zero config (no
 // path matches, so no CORS headers). The config is validated: credentials
 // with a "*" origin, an origin pattern that does not compile and a pattern
-// still wrapped in PHP delimiters (#^...$#) are errors naming the key.
+// still wrapped in PHP delimiters (#^...$#) are errors naming the key. With
+// credentials, a wildcard origin must be the whole leftmost host label
+// (https://*.example.com), a pattern must be anchored with ^ and $, and no
+// origin rule may match an origin outside the configured domains.
 func LoadCORSConfig(cfg *compass.Config) (CORSConfig, error) {
 	var out CORSConfig
 	if cfg == nil || !cfg.Has("http.cors") {
@@ -50,13 +54,111 @@ func validateCORSConfig(prefix string, cfg CORSConfig) error {
 		if phpDelimited(p) {
 			return fmt.Errorf("surf: %s.allowed_origins_patterns[%d] %q is wrapped in PHP delimiters; drop the leading and trailing %q (and any flags): Go patterns take none", prefix, i, p, p[:1])
 		}
-		if _, err := regexp.Compile(p); err != nil {
+		re, err := regexp.Compile(p)
+		if err != nil {
 			return fmt.Errorf("surf: %s.allowed_origins_patterns[%d] %q does not compile: %v", prefix, i, p, err)
 		}
+		if !cfg.SupportsCredentials {
+			continue
+		}
+		if !anchoredOriginPattern(p) {
+			return fmt.Errorf("surf: %s.allowed_origins_patterns[%d] %q is not anchored: with %s.supports_credentials true a pattern must start with ^ and end with $, as in ^https://[a-z]+\\.example\\.com$, or it matches inside any origin", prefix, i, p, prefix)
+		}
+		if probe, ok := matchesCORSProbe(re); ok {
+			return fmt.Errorf("surf: %s.allowed_origins_patterns[%d] %q matches %s, an origin outside any configured domain: with %s.supports_credentials true a pattern must name your own domains", prefix, i, p, probe, prefix)
+		}
+	}
+	if !cfg.SupportsCredentials {
+		return nil
+	}
+	for i, o := range cfg.AllowedOrigins {
+		if o == "*" || !strings.Contains(o, "*") {
+			continue
+		}
+		if !wildcardHostLabel(o) {
+			return fmt.Errorf("surf: %s.allowed_origins[%d] %q: with %s.supports_credentials true a wildcard must be the whole leftmost host label after a literal scheme, as in https://*.example.com", prefix, i, o, prefix)
+		}
+		if probe, ok := matchesCORSProbe(regexp.MustCompile(wildcardOriginPattern(o))); ok {
+			return fmt.Errorf("surf: %s.allowed_origins[%d] %q matches %s, an origin outside any configured domain: with %s.supports_credentials true a wildcard must sit in front of your own domain, as in https://*.example.com", prefix, i, o, probe, prefix)
+		}
 	}
 	return nil
 }
 
+// corsProbeOrigins are origins no credentialed origin rule may match: a
+// rule that matches them trusts origins outside the configured domains
+// (https://*, https://*.com, ^https?://.*$).
+var corsProbeOrigins = []string{
+	"https://cors-probe.invalid",
+	"http://cors-probe.invalid",
+	"https://cors-probe.com",
+	"null",
+}
+
+// matchesCORSProbe reports the first probe origin re matches.
+func matchesCORSProbe(re *regexp.Regexp) (string, bool) {
+	for _, probe := range corsProbeOrigins {
+		if re.MatchString(probe) {
+			return probe, true
+		}
+	}
+	return "", false
+}
+
+// wildcardHostLabel reports an allowed_origins entry whose only "*" is the
+// whole leftmost host label after a literal scheme: https://*.example.com.
+func wildcardHostLabel(origin string) bool {
+	scheme, host, ok := strings.Cut(origin, "://")
+	if !ok || scheme == "" || strings.Contains(scheme, "*") {
+		return false
+	}
+	rest, ok := strings.CutPrefix(host, "*.")
+	return ok && rest != "" && !strings.Contains(rest, "*")
+}
+
+// anchoredOriginPattern reports a pattern anchored at both ends: it starts
+// with ^ and ends with $, and every alternative of the parsed expression
+// stays anchored, so ^a|b$ is refused.
+func anchoredOriginPattern(p string) bool {
+	if !strings.HasPrefix(p, "^") || !strings.HasSuffix(p, "$") {
+		return false
+	}
+	re, err := syntax.Parse(p, syntax.Perl)
+	if err != nil {
+		return false
+	}
+	return anchoredAt(re, true) && anchoredAt(re, false)
+}
+
+// anchoredAt reports whether every match of re begins (start true) or ends
+// at the text boundary.
+func anchoredAt(re *syntax.Regexp, start bool) bool {
+	switch re.Op {
+	case syntax.OpBeginText:
+		return start
+	case syntax.OpEndText:
+		return !start
+	case syntax.OpCapture:
+		return anchoredAt(re.Sub[0], start)
+	case syntax.OpConcat:
+		if len(re.Sub) == 0 {
+			return false
+		}
+		if start {
+			return anchoredAt(re.Sub[0], start)
+		}
+		return anchoredAt(re.Sub[len(re.Sub)-1], start)
+	case syntax.OpAlternate:
+		for _, sub := range re.Sub {
+			if !anchoredAt(sub, start) {
+				return false
+			}
+		}
+		return len(re.Sub) > 0
+	}
+	return false
+}
+
 // phpDelimited reports a preg pattern such as #^https://x$# or /^x$/i: the
 // first byte is # or /, the same byte closes the pattern and only flag
 // letters follow it. An origin pattern never starts with either byte.
diff --git a/modules/surf/cors_profile_test.go b/modules/surf/cors_profile_test.go
index 8dbbfbc..8d2d246 100644
--- a/modules/surf/cors_profile_test.go
+++ b/modules/surf/cors_profile_test.go
@@ -71,6 +71,25 @@ cors:
 `)); err != nil {
 		t.Fatalf("credentials with exact origins: %v", err)
 	}
+
+	// A wildcard host and an unanchored pattern are the same exposure under
+	// another spelling (WR-04): refused with credentials, loaded without.
+	for _, tc := range []struct{ key, value, want string }{
+		{"allowed_origins", "https://*", "http.cors.allowed_origins[1]"},
+		{"allowed_origins_patterns", `https://.*\.example\.com`, "http.cors.allowed_origins_patterns[1]"},
+	} {
+		list := `["https://www.example.com", '` + tc.value + `']`
+		if tc.key == "allowed_origins_patterns" {
+			list = `['^https://www\.example\.com$', '` + tc.value + `']`
+		}
+		yaml := "cors:\n  paths: [\"api/*\"]\n  " + tc.key + ": " + list + "\n"
+		if _, err := LoadCORSConfig(writeHTTPConfig(t, yaml+"  supports_credentials: true\n")); err == nil || !strings.Contains(err.Error(), tc.want) {
+			t.Errorf("%s with credentials: error = %v, want one naming %s", tc.value, err, tc.want)
+		}
+		if _, err := LoadCORSConfig(writeHTTPConfig(t, yaml)); err != nil {
+			t.Errorf("%s without credentials: %v", tc.value, err)
+		}
+	}
 }
 
 func TestCORSPatternErrors(t *testing.T) {