diff --git a/crates/platform/src/serve.rs b/crates/platform/src/serve.rs
index 45a4eb40..ad7524d4 100644
--- a/crates/platform/src/serve.rs
+++ b/crates/platform/src/serve.rs
@@ -134,9 +134,26 @@ fn handle(mut stream: TcpStream, root: &Path) -> std::io::Result<()> {
     reader.read_line(&mut line)?;
     // Drain the headers (bounded by `take`).
     let mut h = String::new();
+    let (mut hosts, mut origins) = (Vec::new(), Vec::new());
     while reader.read_line(&mut h)? > 2 {
+        if let Some((name, value)) = h.trim_end_matches(['\r', '\n']).split_once(':') {
+            if name.eq_ignore_ascii_case("host") {
+                hosts.push(value.trim().to_string());
+            }
+            if name.eq_ignore_ascii_case("origin") {
+                origins.push(value.trim().to_string());
+            }
+        }
         h.clear();
     }
+    if hosts.len() != 1 || origins.len() > 1 {
+        return stream.write_all(b"HTTP/1.1 400 Bad Request\r\nContent-Length: 0\r\nConnection: close\r\n\r\n");
+    }
+    if !hosts.first().is_some_and(|h| crate::standin_server::host_is_loopback(h, Some(stream.local_addr().map_or(0, |a| a.port()))))
+        || origins.first().is_some_and(|o| !crate::standin_server::origin_is_local(o))
+    {
+        return stream.write_all(b"HTTP/1.1 403 Forbidden\r\nContent-Length: 0\r\nConnection: close\r\n\r\n");
+    }
     let mut parts = line.split_whitespace();
     let (method, target) = (parts.next().unwrap_or_default(), parts.next().unwrap_or("/"));
     if method != "GET" && method != "HEAD" {
@@ -176,7 +193,7 @@ mod tests {
 
     fn get(port: u16, path: &str) -> String {
         let mut s = TcpStream::connect(("127.0.0.1", port)).unwrap();
-        s.write_all(format!("GET {path} HTTP/1.1\r\nHost: x\r\n\r\n").as_bytes()).unwrap();
+        s.write_all(format!("GET {path} HTTP/1.1\r\nHost: 127.0.0.1:{port}\r\n\r\n").as_bytes()).unwrap();
         let mut out = String::new();
         s.read_to_string(&mut out).unwrap();
         out
diff --git a/crates/platform/tests/regression_preview_local_host.rs b/crates/platform/tests/regression_preview_local_host.rs
new file mode 100644
index 00000000..7d0bd4ba
--- /dev/null
+++ b/crates/platform/tests/regression_preview_local_host.rs
@@ -0,0 +1,50 @@
+use craft_anything_platform::serve::serve_dir;
+use std::io::{Read, Write};
+use std::net::TcpStream;
+use std::time::Duration;
+fn get(port: u16, path: &str) -> String {
+    let mut s = TcpStream::connect(("127.0.0.1", port)).unwrap();
+    s.set_read_timeout(Some(Duration::from_secs(10))).unwrap();
+    s.write_all(format!("GET {path} HTTP/1.1\r\nHost: 127.0.0.1:{port}\r\n\r\n").as_bytes()).unwrap();
+    let mut out = String::new();
+    s.read_to_string(&mut out).unwrap();
+    out
+}
+
+#[test]
+fn regression_preview_refuses_foreign_hosts_and_origins() {
+    let dir = tempfile::tempdir().unwrap();
+    std::fs::write(dir.path().join("index.html"), "local-only-content").unwrap();
+    let srv = serve_dir(dir.path()).unwrap();
+    for extra in [
+        "Host: attacker.example\r\n".to_string(),
+        "Host: localhost.attacker.example\r\n".to_string(),
+        format!("Host: localhost:{}\r\nOrigin: https://attacker.example\r\n", srv.port),
+        format!("Host: localhost:{}\r\nHost: attacker.example\r\n", srv.port),
+        format!("Host: localhost:{}\r\nOrigin: http://localhost:3000\r\nOrigin: https://attacker.example\r\n", srv.port),
+    ] {
+        let mut s = TcpStream::connect(("127.0.0.1", srv.port)).unwrap();
+        s.set_read_timeout(Some(Duration::from_secs(10))).unwrap();
+        s.write_all(format!("GET / HTTP/1.1\r\n{extra}\r\n").as_bytes()).unwrap();
+        let mut out = String::new();
+        s.read_to_string(&mut out).unwrap();
+        assert!(out.starts_with("HTTP/1.1 400") || out.starts_with("HTTP/1.1 403"), "{out}");
+        assert!(!out.contains("local-only-content"));
+    }
+    assert!(get(srv.port, "/").contains("local-only-content"));
+}
+
+#[test]
+fn regression_preview_accepts_a_local_origin() {
+    let dir = tempfile::tempdir().unwrap();
+    std::fs::write(dir.path().join("index.html"), "local-only-content").unwrap();
+    let srv = serve_dir(dir.path()).unwrap();
+    let mut stream = TcpStream::connect(("127.0.0.1", srv.port)).unwrap();
+    stream.set_read_timeout(Some(Duration::from_secs(10))).unwrap();
+    stream.write_all(format!("GET / HTTP/1.1\r\nHost: 127.0.0.1:{}\r\nOrigin: http://localhost:3000\r\n\r\n", srv.port).as_bytes()).unwrap();
+    let mut response = String::new();
+    stream.read_to_string(&mut response).unwrap();
+    let (headers, body) = response.split_once("\r\n\r\n").unwrap();
+    assert!(headers.starts_with("HTTP/1.1 200 "), "{headers}");
+    assert_eq!(body, "local-only-content");
+}