diff --git a/src/api/client/membership/join.rs b/src/api/client/membership/join.rs
index 953211a1..2d16a70e 100644
--- a/src/api/client/membership/join.rs
+++ b/src/api/client/membership/join.rs
@@ -48,7 +48,7 @@ use service::{
 	},
 };
 
-use super::banned_room_check;
+use super::{banned_room_check, validate_remote_member_event_stub};
 use crate::Ruma;
 
 /// # `POST /_matrix/client/r0/rooms/{roomId}/join`
@@ -837,6 +837,13 @@ async fn join_room_by_id_helper_local(
 			err!(BadServerResponse("Invalid make_join event json received from server: {e:?}"))
 		})?;
 
+	validate_remote_member_event_stub(
+		&MembershipState::Join,
+		sender_user,
+		room_id,
+		&join_event_stub,
+	)?;
+
 	let join_authorized_via_users_server = join_event_stub
 		.get("content")
 		.map(|s| {
diff --git a/src/api/client/membership/knock.rs b/src/api/client/membership/knock.rs
index 39db96d0..0ecbe2f5 100644
--- a/src/api/client/membership/knock.rs
+++ b/src/api/client/membership/knock.rs
@@ -38,7 +38,7 @@ use service::{
 	},
 };
 
-use super::{banned_room_check, join::join_room_by_id_helper};
+use super::{banned_room_check, join::join_room_by_id_helper, validate_remote_member_event_stub};
 use crate::Ruma;
 
 /// # `POST /_matrix/client/*/knock/{roomIdOrAlias}`
@@ -408,6 +408,13 @@ async fn knock_room_helper_local(
 		err!(BadServerResponse("Invalid make_knock event json received from server: {e:?}"))
 	})?;
 
+	validate_remote_member_event_stub(
+		&MembershipState::Knock,
+		sender_user,
+		room_id,
+		&knock_event_stub,
+	)?;
+
 	knock_event_stub.insert(
 		"origin".to_owned(),
 		CanonicalJsonValue::String(services.globals.server_name().as_str().to_owned()),
diff --git a/src/api/client/membership/leave.rs b/src/api/client/membership/leave.rs
index 4ef4a2b0..90fbbb86 100644
--- a/src/api/client/membership/leave.rs
+++ b/src/api/client/membership/leave.rs
@@ -21,6 +21,7 @@ use ruma::{
 };
 use service::Services;
 
+use super::validate_remote_member_event_stub;
 use crate::Ruma;
 
 /// # `POST /_matrix/client/v3/rooms/{roomId}/leave`
@@ -324,6 +325,13 @@ pub async fn remote_leave_room<S: ::std::hash::BuildHasher>(
 		)))
 	})?;
 
+	validate_remote_member_event_stub(
+		&MembershipState::Leave,
+		user_id,
+		room_id,
+		&leave_event_stub,
+	)?;
+
 	// TODO: Is origin needed?
 	leave_event_stub.insert(
 		"origin".to_owned(),
diff --git a/src/api/client/membership/mod.rs b/src/api/client/membership/mod.rs
index 5e742a69..9123bac8 100644
--- a/src/api/client/membership/mod.rs
+++ b/src/api/client/membership/mod.rs
@@ -13,7 +13,14 @@ use std::net::IpAddr;
 use axum::extract::State;
 use conduwuit::{Err, Result, warn};
 use futures::{FutureExt, StreamExt};
-use ruma::{OwnedRoomId, RoomId, ServerName, UserId, api::client::membership::joined_rooms};
+use ruma::{
+	CanonicalJsonObject, OwnedRoomId, RoomId, ServerName, UserId,
+	api::client::membership::joined_rooms,
+	events::{
+		StaticEventContent,
+		room::member::{MembershipState, RoomMemberEventContent},
+	},
+};
 use service::Services;
 
 pub(crate) use self::{
@@ -153,3 +160,80 @@ pub(crate) async fn banned_room_check(
 
 	Ok(())
 }
+
+/// Validates that an event returned from a remote server by `/make_*`
+/// actually is a membership event with the expected fields.
+///
+/// Without checking this, the remote server could use the remote membership
+/// mechanism to trick our server into signing arbitrary malicious events.
+pub(crate) fn validate_remote_member_event_stub(
+	membership: &MembershipState,
+	user_id: &UserId,
+	room_id: &RoomId,
+	event_stub: &CanonicalJsonObject,
+) -> Result<()> {
+	let Some(event_type) = event_stub.get("type") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing type field"
+		));
+	};
+	if event_type != &RoomMemberEventContent::TYPE {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with invalid event type"
+		));
+	}
+
+	let Some(sender) = event_stub.get("sender") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing sender field"
+		));
+	};
+	if sender != &user_id.as_str() {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with incorrect sender"
+		));
+	}
+
+	let Some(state_key) = event_stub.get("state_key") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing state_key field"
+		));
+	};
+	if state_key != &user_id.as_str() {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with incorrect state_key"
+		));
+	}
+
+	let Some(event_room_id) = event_stub.get("room_id") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing room_id field"
+		));
+	};
+	if event_room_id != &room_id.as_str() {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with incorrect room_id"
+		));
+	}
+
+	let Some(content) = event_stub
+		.get("content")
+		.and_then(|content| content.as_object())
+	else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing content field"
+		));
+	};
+	let Some(event_membership) = content.get("membership") else {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with missing membership field"
+		));
+	};
+	if event_membership != &membership.as_str() {
+		return Err!(BadServerResponse(
+			"Remote server returned member event with incorrect room_id"
+		));
+	}
+
+	Ok(())
+}