fix: harden cluster key rate limit cookie parsing (#4012)

Signed-off-by: EndlessSeeker <1766508902@qq.com>

plugins/wasm-go/extensions/cluster-key-rate-limit/util/utils.go

@@ -50,8 +50,8 @@ func ExtractCookieValueByKey(cookie string, key string) (value string) {
 	pairs := strings.Split(cookie, ";")
 	for _, pair := range pairs {
 		pair = strings.TrimSpace(pair)
-		kv := strings.Split(pair, "=")
-		if kv[0] == key {
+		kv := strings.SplitN(pair, "=", 2)
+		if len(kv) == 2 && kv[0] == key {
 			value = kv[1]
 			break
 		}