diff --git a/src/channels.rs b/src/channels.rs
index 8b98492..01eb7cd 100644
--- a/src/channels.rs
+++ b/src/channels.rs
@@ -1288,7 +1288,8 @@ pub fn normalize_ban_mask(m: &str) -> String {
     if b.len() >= 2 && b[1] == b':' && (b[0] as char).is_ascii_alphabetic() {
         // These extbans carry a name / spec / channel / server, not a host mask,
         // so they must not be host-normalised: g: (security group), y: (reputation
-        // score), r: (realname), j: (channel), s: (server name).
+        // score), r: (realname), j: (channel), s: (server name), G: (country),
+        // b: (banned-in-channel).
         if matches!(b[0], b'g' | b'y' | b'r' | b'j' | b's' | b'G' | b'b') {
             return m.to_string();
         }
diff --git a/src/http.rs b/src/http.rs
index 9ceeb3c..40bcd80 100644
--- a/src/http.rs
+++ b/src/http.rs
@@ -84,19 +84,24 @@ pub fn post(
 /// Decode an HTTP/1.1 chunked body (best effort). Used for both outbound response
 /// bodies here and inbound request bodies in the RPC httpd.
 pub fn dechunk(body: &str) -> String {
-    let mut out = String::new();
-    let mut rest = body;
-    while let Some((size_line, after)) = rest.split_once("\r\n") {
-        let size = usize::from_str_radix(size_line.trim().split(';').next().unwrap_or("0"), 16)
+    // Work on bytes, not the &str: the chunk size is an attacker-supplied byte
+    // count and may land mid-UTF-8-character, so str slicing would panic.
+    let mut out: Vec<u8> = Vec::new();
+    let mut rest = body.as_bytes();
+    while let Some(nl) = rest.windows(2).position(|w| w == b"\r\n") {
+        let size = std::str::from_utf8(&rest[..nl])
+            .ok()
+            .and_then(|s| usize::from_str_radix(s.trim().split(';').next().unwrap_or("0"), 16).ok())
             .unwrap_or(0);
+        let after = &rest[nl + 2..];
         if size == 0 || after.len() < size {
-            out.push_str(&after[..after.len().min(size)]);
+            out.extend_from_slice(&after[..after.len().min(size)]);
             break;
         }
-        out.push_str(&after[..size]);
-        rest = after[size..].strip_prefix("\r\n").unwrap_or(&after[size..]);
+        out.extend_from_slice(&after[..size]);
+        rest = after[size..].strip_prefix(b"\r\n").unwrap_or(&after[size..]);
     }
-    out
+    String::from_utf8_lossy(&out).into_owned()
 }
 
 /// application/x-www-form-urlencoded escape of a single value.
diff --git a/src/ircd.rs b/src/ircd.rs
index 349de26..9f9aaac 100644
--- a/src/ircd.rs
+++ b/src/ircd.rs
@@ -160,6 +160,10 @@ impl Ircd {
             {
                 // the default panic hook already logged the details to stderr
                 eprintln!("[core] recovered from a panicking event handler; continuing");
+                // a panic mid-handler can leave transient per-command state set;
+                // clear it so it doesn't corrupt the next command
+                self.server.label_capture.borrow_mut().take();
+                self.server.mode_sudo = false;
             }
             busy.store(0, Ordering::Relaxed);
             let ms = start.elapsed().as_millis() as u64;
diff --git a/src/link.rs b/src/link.rs
index d79d43a..39c5607 100644
--- a/src/link.rs
+++ b/src/link.rs
@@ -898,6 +898,12 @@ impl Server {
         let Some(newnick) = msg.params.first().cloned() else {
             return;
         };
+        // collision with a local user: kill the local holder (same policy as an
+        // incoming UID clash) so the network converges to one owner for the nick
+        if let Some(luid) = self.find_nick(&newnick) {
+            self.send(luid, "ERROR :Closing link: Nick collision".to_string());
+            self.remove_user(luid, "Nick collision");
+        }
         let old = match self.remote_users.get_mut(&uuid) {
             Some(ru) => {
                 let old = ru.nick.clone();
@@ -1411,7 +1417,7 @@ impl Server {
         let chan = msg.params[0].clone();
         let key = chan.to_ascii_lowercase();
         let victim = msg.params[1].clone();
-        let reason = msg.params.get(2).cloned().unwrap_or_else(|| victim.clone());
+        let reason = msg.params.get(2).cloned().unwrap_or_default();
         let prefix = self.uuid_prefix(&src).unwrap_or_default();
         let mut removed = false;
         let vnick;
@@ -1694,6 +1700,15 @@ impl Server {
                 ch.modes.render(false),
                 mem.join(" ")
             ));
+            // render(false) puts parametric mode letters in the FJOIN without their
+            // values; burst the access-controlling ones (key, limit) as timestamped
+            // FMODEs so they survive netburst (the receiver's FMODE path is param-aware)
+            if let Some(k) = &ch.modes.key {
+                lines.push(format!(":{} FMODE {} {} +k {}", self.sid, ch.name, ch.created, k));
+            }
+            if let Some(l) = ch.modes.limit {
+                lines.push(format!(":{} FMODE {} {} +l {}", self.sid, ch.name, ch.created, l));
+            }
             // burst the ban / except / invite-exception lists as timestamped mode
             // changes sourced from this server
             for (letter, list) in [('b', &ch.bans), ('e', &ch.excepts), ('I', &ch.invex)] {
diff --git a/src/modules/blockamsg.rs b/src/modules/blockamsg.rs
index 1aa0402..74a136a 100644
--- a/src/modules/blockamsg.rs
+++ b/src/modules/blockamsg.rs
@@ -28,6 +28,11 @@ impl Module for BlockAmsg {
     fn name(&self) -> &'static str {
         "blockamsg"
     }
+    fn on_user_quit(&mut self, s: &mut Server, uid: Uid, _reason: &str) {
+        if let Some(m) = s.ext.get_mut::<LastMsg>() {
+            m.0.remove(&uid);
+        }
+    }
 
     fn on_pre_command(
         &mut self,
diff --git a/src/modules/cloudflare_challenge.rs b/src/modules/cloudflare_challenge.rs
index a79a7c9..e198c5b 100644
--- a/src/modules/cloudflare_challenge.rs
+++ b/src/modules/cloudflare_challenge.rs
@@ -62,6 +62,11 @@ impl Module for CloudflareChallenge {
     fn name(&self) -> &'static str {
         "cloudflare_challenge"
     }
+    fn on_user_quit(&mut self, s: &mut Server, uid: Uid, _reason: &str) {
+        if let Some(p) = s.ext.get_mut::<Passed>() {
+            p.0.remove(&uid);
+        }
+    }
 
     fn on_user_register(&mut self, srv: &mut Server, uid: Uid) -> ModResult {
         if !enabled(srv) || srv.is_oper(uid) {
diff --git a/src/modules/recaptcha.rs b/src/modules/recaptcha.rs
index d65a5f8..480df32 100644
--- a/src/modules/recaptcha.rs
+++ b/src/modules/recaptcha.rs
@@ -71,6 +71,11 @@ impl Module for ReCaptcha {
     fn name(&self) -> &'static str {
         "recaptcha"
     }
+    fn on_user_quit(&mut self, s: &mut Server, uid: Uid, _reason: &str) {
+        if let Some(v) = s.ext.get_mut::<Verified>() {
+            v.0.remove(&uid);
+        }
+    }
 
     fn on_user_register(&mut self, srv: &mut Server, uid: Uid) -> ModResult {
         if !enabled(srv) || srv.is_oper(uid) {
diff --git a/src/modules/rpc/message.rs b/src/modules/rpc/message.rs
index a5ed34b..7c8ecde 100644
--- a/src/modules/rpc/message.rs
+++ b/src/modules/rpc/message.rs
@@ -12,6 +12,9 @@ pub fn handle(s: &mut Server, action: &str, params: &str) -> Result<String, RpcE
                 .ok_or_else(|| RpcError::invalid_params("missing 'target'"))?;
             let text = json::get_str(params, "message")
                 .ok_or_else(|| RpcError::invalid_params("missing 'message'"))?;
+            // strip CR/LF so a crafted message/target can't inject extra IRC lines
+            let strip = |v: String| -> String { v.chars().filter(|c| *c != '\r' && *c != '\n').collect() };
+            let (target, text) = (strip(target), strip(text));
             let src = s.name.clone();
             if target == "*" || target == "$*" {
                 let uids: Vec<crate::Uid> = s.users.keys().copied().collect();
diff --git a/src/modules/rpc/user.rs b/src/modules/rpc/user.rs
index c881ddf..8ba2dde 100644
--- a/src/modules/rpc/user.rs
+++ b/src/modules/rpc/user.rs
@@ -107,6 +107,9 @@ pub fn handle(s: &mut Server, action: &str, params: &str) -> Result<String, RpcE
             let host = json::get_str(params, "vhost")
                 .or_else(|| json::get_str(params, "host"))
                 .ok_or_else(|| RpcError::invalid_params("missing 'vhost'"))?;
+            if !crate::users::valid_host(&host) {
+                return Err(RpcError::invalid_params("invalid vhost"));
+            }
             s.change_host_ident(uid, None, Some(&host));
             Ok(obj(&[("result", "true".into())]))
         }
@@ -114,6 +117,16 @@ pub fn handle(s: &mut Server, action: &str, params: &str) -> Result<String, RpcE
             let uid = resolve(s, params).ok_or_else(|| RpcError::not_found("no such user"))?;
             let newnick = json::get_str(params, "newnick")
                 .ok_or_else(|| RpcError::invalid_params("missing 'newnick'"))?;
+            // validate + collision-check like the NICK / SVSNICK paths: an invalid or
+            // taken nick would otherwise inject into the wire or hijack the nick index
+            if !crate::users::valid_nick(&newnick, s.conf_num("maxnick", 30usize)) {
+                return Err(RpcError::invalid_params("invalid nick"));
+            }
+            if s.find_nick(&newnick).is_some_and(|o| o != uid)
+                || s.remote_nick.contains_key(&newnick.to_ascii_lowercase())
+            {
+                return Err(RpcError::invalid_params("nick in use"));
+            }
             s.set_nick(uid, &newnick);
             Ok(obj(&[("result", "true".into())]))
         }
diff --git a/src/server.rs b/src/server.rs
index b2f0661..bc225ac 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -73,6 +73,17 @@ pub fn parse_iso(s: &str) -> Option<u64> {
     let h: i64 = t.next()?.parse().ok()?;
     let mi: i64 = t.next()?.parse().ok()?;
     let se: i64 = t.next().unwrap_or("0").parse().ok()?;
+    // bound every field to a sane range: keeps the arithmetic below well inside i64
+    // (a client-supplied huge year/day would otherwise overflow and panic)
+    if !(0..=9999).contains(&y)
+        || !(1..=12).contains(&mo)
+        || !(1..=31).contains(&da)
+        || !(0..=23).contains(&h)
+        || !(0..=59).contains(&mi)
+        || !(0..=60).contains(&se)
+    {
+        return None;
+    }
     // civil date -> days since 1970-01-01
     let yy = y - i64::from(mo <= 2);
     let era = if yy >= 0 { yy } else { yy - 399 } / 400;
@@ -255,6 +266,7 @@ impl Server {
         self.dnsbl_action = fresh.dnsbl_action;
         self.dnsbl_reason = fresh.dnsbl_reason;
         self.sasl_server = fresh.sasl_server;
+        self.webirc = fresh.webirc;
         self.raw_config = fresh.raw;
     }
 
diff --git a/src/websocket.rs b/src/websocket.rs
index 1fd918c..e356110 100644
--- a/src/websocket.rs
+++ b/src/websocket.rs
@@ -402,6 +402,12 @@ fn deliver(msg: &mut Vec<u8>, uid: Uid, core: &Sender<Event>) -> bool {
     let text = String::from_utf8_lossy(msg);
     for piece in text.split('\n') {
         let l = piece.trim_end_matches('\r');
+        // a WS frame can be far larger than a legal IRC line; drop an over-long
+        // line so the transport can't bypass the recvq/max-line flood guard that
+        // every TCP/TLS client is held to (16 KiB is generous — tags included)
+        if l.len() > 16 * 1024 {
+            continue;
+        }
         if !l.is_empty()
             && core
                 .send(Event::Line {
diff --git a/src/xline.rs b/src/xline.rs
index f5030d3..1e0b360 100644
--- a/src/xline.rs
+++ b/src/xline.rs
@@ -69,7 +69,9 @@ pub fn parse_duration(s: &str) -> Option<u64> {
     if last.is_ascii_digit() {
         return s.parse::<u64>().ok();
     }
-    let n: u64 = s[..s.len() - 1].parse().ok()?;
+    // strip the suffix by its char length, not one byte — a multi-byte final char
+    // (e.g. "5€") would otherwise slice mid-codepoint and panic
+    let n: u64 = s[..s.len() - last.len_utf8()].parse().ok()?;
     let mul = match last {
         's' => 1,
         'm' => 60,