diff --git a/CHANGELOG.md b/CHANGELOG.md
index cd246ca4..ec3389e7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,16 @@
+## 0.21.0-rc.0 / 2022-05-10
+
+This Prometheus release is built with go1.18, which contains two noticeable
+changes related to TLS and HTTP:
+
+1. [TLS 1.0 and 1.1 disabled by default client-side](https://go.dev/doc/go1.18#tls10).
+   Blackbox Exporter users can override this with the `min_version` parameter of
+   [tls_config](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#tls_config).
+2. [Certificates signed with the SHA-1 hash function are rejected](https://go.dev/doc/go1.18#sha1).
+   This doesn't apply to self-signed root certificates.
+
+* [BUGFIX] Prevent setting negative timeouts when using a small scrape interval. #869
+
 ## 0.20.0 / 2022-03-16
 
 * [FEATURE] Add support for grpc health check. #835
diff --git a/CONFIGURATION.md b/CONFIGURATION.md
index 441b0262..6de22380 100644
--- a/CONFIGURATION.md
+++ b/CONFIGURATION.md
@@ -118,6 +118,9 @@ The other placeholders are specified separately.
   oauth2:
       [ <oauth2> ]
 
+  # Whether to enable HTTP2.
+  [ enable_http2: <bool> | default: true ]
+
   # The IP protocol of the HTTP probe (ip4, ip6).
   [ preferred_ip_protocol: <string> | default = "ip6" ]
   [ ip_protocol_fallback: <boolean> | default = true ]
@@ -298,6 +301,11 @@ tls_config:
 # Used to verify the hostname for the targets.
 [ server_name: <string> ]
 
+# Minimum acceptable TLS version. Accepted values: TLS10 (TLS 1.0), TLS11 (TLS
+# 1.1), TLS12 (TLS 1.2), TLS13 (TLS 1.3).
+# If unset, Prometheus will use Go default minimum version, which is TLS 1.2.
+# See MinVersion in https://pkg.go.dev/crypto/tls#Config.
+[ min_version: <string> ]
 ```
 
 #### <oauth2>
diff --git a/VERSION b/VERSION
index 5a03fb73..60e5ebac 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-0.20.0
+0.21.0-rc.0
diff --git a/go.mod b/go.mod
index 67e80875..de43062e 100644
--- a/go.mod
+++ b/go.mod
@@ -27,7 +27,7 @@ require (
 	github.com/matttproud/golang_protobuf_extensions v1.0.1 // indirect
 	github.com/mwitkow/go-conntrack v0.0.0-20190716064945-2f068394615f // indirect
 	github.com/prometheus/procfs v0.7.3 // indirect
-	golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e // indirect
+	golang.org/x/crypto v0.0.0-20220427172511-eb4f295cb31f // indirect
 	golang.org/x/mod v0.4.2 // indirect
 	golang.org/x/oauth2 v0.0.0-20220223155221-ee480838109b // indirect
 	golang.org/x/sys v0.0.0-20220114195835-da31bd327af9 // indirect
diff --git a/go.sum b/go.sum
index 8bae8d2a..8658f43b 100644
--- a/go.sum
+++ b/go.sum
@@ -238,8 +238,9 @@ golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8U
 golang.org/x/crypto v0.0.0-20190605123033-f99c8df09eb5/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
-golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e h1:gsTQYXdTw2Gq7RBsWvlQ91b+aEQ6bXFUngBGuR8sPpI=
 golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/crypto v0.0.0-20220427172511-eb4f295cb31f h1:OeJjE6G4dgCY4PIXvIRQbE8+RX+uXZyGhUy/ksMGJoc=
+golang.org/x/crypto v0.0.0-20220427172511-eb4f295cb31f/go.mod h1:IxCIyHEi3zRg3s0A5j5BB6A9Jmi73HwBIUl50j+osU4=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190510132918-efd6b22b2522/go.mod h1:ZjyILWgesfNpC6sMxTJOJm9Kp84zZh5NQWvqDGG3Qr8=
@@ -305,6 +306,7 @@ golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v
 golang.org/x/net v0.0.0-20210405180319-a5a99cb37ef4/go.mod h1:p54w0d4576C0XHj96bSt6lcn1PtDYWL6XObtHCRCNQM=
 golang.org/x/net v0.0.0-20210525063256-abc453219eb5/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
 golang.org/x/net v0.0.0-20210726213435-c6fcb2dbf985/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
+golang.org/x/net v0.0.0-20211112202133-69e39bad7dc2/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
 golang.org/x/net v0.0.0-20220127200216-cd36cc0744dd/go.mod h1:CfG3xpIq0wQ8r1q4Su4UZFWDARRcnwPjda9FqA0JpMk=
 golang.org/x/net v0.0.0-20220225172249-27dd8689420f/go.mod h1:CfG3xpIq0wQ8r1q4Su4UZFWDARRcnwPjda9FqA0JpMk=
 golang.org/x/net v0.0.0-20220425223048-2871e0cb64e4 h1:HVyaeDAYux4pnY+D/SiwmLOR36ewZ4iGQIIrtnuCjFA=