diff --git a/api/openapi-spec/swagger.json b/api/openapi-spec/swagger.json
index cb5b5d68ca4..245fe7501a2 100644
--- a/api/openapi-spec/swagger.json
+++ b/api/openapi-spec/swagger.json
@@ -68056,7 +68056,7 @@
       "$ref": "#/definitions/io.k8s.api.admissionregistration.v1alpha1.ServiceReference"
      },
      "url": {
-      "description": "`url` gives the location of the webhook, in standard URL form (`[scheme://]host:port/path`). Exactly one of `url` or `service` must be specified.\n\nThe `host` should not refer to a service running in the cluster; use the `service` field instead. The host might be resolved via external DNS in some apiservers (e.g., `kube-apiserver` cannot resolve in-cluster DNS as that would be a layering violation). `host` may also be an IP address.\n\nPlease note that using `localhost` or `127.0.0.1` as a `host` is risky unless you take great care to run this webhook on all hosts which run an apiserver which might need to make calls to this webhook. Such installs are likely to be non-portable, i.e., not easy to turn up in a new cluster.\n\nIf the scheme is present, it must be \"https://\".\n\nA path is optional, and if present may be any string permissible in a URL. You may use the path to pass an arbitrary string to the webhook, for example, a cluster identifier.",
+      "description": "`url` gives the location of the webhook, in standard URL form (`[scheme://]host:port/path`). Exactly one of `url` or `service` must be specified.\n\nThe `host` should not refer to a service running in the cluster; use the `service` field instead. The host might be resolved via external DNS in some apiservers (e.g., `kube-apiserver` cannot resolve in-cluster DNS as that would be a layering violation). `host` may also be an IP address.\n\nPlease note that using `localhost` or `127.0.0.1` as a `host` is risky unless you take great care to run this webhook on all hosts which run an apiserver which might need to make calls to this webhook. Such installs are likely to be non-portable, i.e., not easy to turn up in a new cluster.\n\nThe scheme must be \"https\"; the URL must begin with \"https://\".\n\nA path is optional, and if present may be any string permissible in a URL. You may use the path to pass an arbitrary string to the webhook, for example, a cluster identifier.\n\nAttempting to use a user or basic auth e.g. \"user:password@\" is not allowed. Fragments (\"#...\") and query parameters (\"?...\") are not allowed, either.",
       "type": "string"
      }
     }
diff --git a/api/swagger-spec/admissionregistration.k8s.io_v1alpha1.json b/api/swagger-spec/admissionregistration.k8s.io_v1alpha1.json
index e80847ccef6..a2b65c8a9be 100644
--- a/api/swagger-spec/admissionregistration.k8s.io_v1alpha1.json
+++ b/api/swagger-spec/admissionregistration.k8s.io_v1alpha1.json
@@ -2636,7 +2636,7 @@
     "properties": {
      "url": {
       "type": "string",
-      "description": "`url` gives the location of the webhook, in standard URL form (`[scheme://]host:port/path`). Exactly one of `url` or `service` must be specified.\n\nThe `host` should not refer to a service running in the cluster; use the `service` field instead. The host might be resolved via external DNS in some apiservers (e.g., `kube-apiserver` cannot resolve in-cluster DNS as that would be a layering violation). `host` may also be an IP address.\n\nPlease note that using `localhost` or `127.0.0.1` as a `host` is risky unless you take great care to run this webhook on all hosts which run an apiserver which might need to make calls to this webhook. Such installs are likely to be non-portable, i.e., not easy to turn up in a new cluster.\n\nIf the scheme is present, it must be \"https://\".\n\nA path is optional, and if present may be any string permissible in a URL. You may use the path to pass an arbitrary string to the webhook, for example, a cluster identifier."
+      "description": "`url` gives the location of the webhook, in standard URL form (`[scheme://]host:port/path`). Exactly one of `url` or `service` must be specified.\n\nThe `host` should not refer to a service running in the cluster; use the `service` field instead. The host might be resolved via external DNS in some apiservers (e.g., `kube-apiserver` cannot resolve in-cluster DNS as that would be a layering violation). `host` may also be an IP address.\n\nPlease note that using `localhost` or `127.0.0.1` as a `host` is risky unless you take great care to run this webhook on all hosts which run an apiserver which might need to make calls to this webhook. Such installs are likely to be non-portable, i.e., not easy to turn up in a new cluster.\n\nThe scheme must be \"https\"; the URL must begin with \"https://\".\n\nA path is optional, and if present may be any string permissible in a URL. You may use the path to pass an arbitrary string to the webhook, for example, a cluster identifier.\n\nAttempting to use a user or basic auth e.g. \"user:password@\" is not allowed. Fragments (\"#...\") and query parameters (\"?...\") are not allowed, either."
      },
      "service": {
       "$ref": "v1alpha1.ServiceReference",
diff --git a/docs/api-reference/admissionregistration.k8s.io/v1alpha1/definitions.html b/docs/api-reference/admissionregistration.k8s.io/v1alpha1/definitions.html
index 6cd52cfce3f..61d0624657d 100755
--- a/docs/api-reference/admissionregistration.k8s.io/v1alpha1/definitions.html
+++ b/docs/api-reference/admissionregistration.k8s.io/v1alpha1/definitions.html
@@ -634,9 +634,11 @@ The <code>host</code> should not refer to a service running in the cluster; use
 <br>
 Please note that using <code>localhost</code> or <code>127.0.0.1</code> as a <code>host</code> is risky unless you take great care to run this webhook on all hosts which run an apiserver which might need to make calls to this webhook. Such installs are likely to be non-portable, i.e., not easy to turn up in a new cluster.<br>
 <br>
-If the scheme is present, it must be "https://".<br>
+The scheme must be "https"; the URL must begin with "https://".<br>
 <br>
-A path is optional, and if present may be any string permissible in a URL. You may use the path to pass an arbitrary string to the webhook, for example, a cluster identifier.</p></td>
+A path is optional, and if present may be any string permissible in a URL. You may use the path to pass an arbitrary string to the webhook, for example, a cluster identifier.<br>
+<br>
+Attempting to use a user or basic auth e.g. "user:password@" is not allowed. Fragments ("#&#8230;") and query parameters ("?&#8230;") are not allowed, either.</p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">false</p></td>
 <td class="tableblock halign-left valign-top"><p class="tableblock">string</p></td>
 <td class="tableblock halign-left valign-top"></td>
diff --git a/staging/src/k8s.io/api/admissionregistration/v1alpha1/generated.proto b/staging/src/k8s.io/api/admissionregistration/v1alpha1/generated.proto
index f450cb4c029..d4b7aa9ae9d 100644
--- a/staging/src/k8s.io/api/admissionregistration/v1alpha1/generated.proto
+++ b/staging/src/k8s.io/api/admissionregistration/v1alpha1/generated.proto
@@ -274,12 +274,16 @@ message WebhookClientConfig {
   // webhook. Such installs are likely to be non-portable, i.e., not easy
   // to turn up in a new cluster.
   // 
-  // If the scheme is present, it must be "https://".
+  // The scheme must be "https"; the URL must begin with "https://".
   // 
   // A path is optional, and if present may be any string permissible in
   // a URL. You may use the path to pass an arbitrary string to the
   // webhook, for example, a cluster identifier.
   // 
+  // Attempting to use a user or basic auth e.g. "user:password@" is not
+  // allowed. Fragments ("#...") and query parameters ("?...") are not
+  // allowed, either.
+  // 
   // +optional
   optional string url = 3;
 
diff --git a/staging/src/k8s.io/api/admissionregistration/v1alpha1/types_swagger_doc_generated.go b/staging/src/k8s.io/api/admissionregistration/v1alpha1/types_swagger_doc_generated.go
index b8bafeb0bc4..6f8defa9968 100644
--- a/staging/src/k8s.io/api/admissionregistration/v1alpha1/types_swagger_doc_generated.go
+++ b/staging/src/k8s.io/api/admissionregistration/v1alpha1/types_swagger_doc_generated.go
@@ -143,7 +143,7 @@ func (Webhook) SwaggerDoc() map[string]string {
 
 var map_WebhookClientConfig = map[string]string{
 	"":         "WebhookClientConfig contains the information to make a TLS connection with the webhook",
-	"url":      "`url` gives the location of the webhook, in standard URL form (`[scheme://]host:port/path`). Exactly one of `url` or `service` must be specified.\n\nThe `host` should not refer to a service running in the cluster; use the `service` field instead. The host might be resolved via external DNS in some apiservers (e.g., `kube-apiserver` cannot resolve in-cluster DNS as that would be a layering violation). `host` may also be an IP address.\n\nPlease note that using `localhost` or `127.0.0.1` as a `host` is risky unless you take great care to run this webhook on all hosts which run an apiserver which might need to make calls to this webhook. Such installs are likely to be non-portable, i.e., not easy to turn up in a new cluster.\n\nIf the scheme is present, it must be \"https://\".\n\nA path is optional, and if present may be any string permissible in a URL. You may use the path to pass an arbitrary string to the webhook, for example, a cluster identifier.",
+	"url":      "`url` gives the location of the webhook, in standard URL form (`[scheme://]host:port/path`). Exactly one of `url` or `service` must be specified.\n\nThe `host` should not refer to a service running in the cluster; use the `service` field instead. The host might be resolved via external DNS in some apiservers (e.g., `kube-apiserver` cannot resolve in-cluster DNS as that would be a layering violation). `host` may also be an IP address.\n\nPlease note that using `localhost` or `127.0.0.1` as a `host` is risky unless you take great care to run this webhook on all hosts which run an apiserver which might need to make calls to this webhook. Such installs are likely to be non-portable, i.e., not easy to turn up in a new cluster.\n\nThe scheme must be \"https\"; the URL must begin with \"https://\".\n\nA path is optional, and if present may be any string permissible in a URL. You may use the path to pass an arbitrary string to the webhook, for example, a cluster identifier.\n\nAttempting to use a user or basic auth e.g. \"user:password@\" is not allowed. Fragments (\"#...\") and query parameters (\"?...\") are not allowed, either.",
 	"service":  "`service` is a reference to the service for this webhook. Either `service` or `url` must be specified.\n\nIf the webhook is running within the cluster, then you should use `service`.\n\nIf there is only one port open for the service, that port will be used. If there are multiple ports open, port 443 will be used if it is open, otherwise it is an error.",
 	"caBundle": "`caBundle` is a PEM encoded CA bundle which will be used to validate the webhook's server certificate. Required.",
 }