diff --git a/rust/core/migrations/009_purge_legacy_secrets.sql b/rust/core/migrations/009_purge_legacy_secrets.sql
new file mode 100644
index 0000000..4cd81f9
--- /dev/null
+++ b/rust/core/migrations/009_purge_legacy_secrets.sql
@@ -0,0 +1,10 @@
+-- Profiles saved by the Go app kept proxyPassword and totpSecret inside ssh_config. They live in
+-- the keychain or vault now and are dropped on read, but the old JSON stayed in the column until
+-- the profile was next saved. Remove them (the store also VACUUMs after this migration so the
+-- old pages don't linger in the file).
+UPDATE profiles
+SET ssh_config = json_remove(ssh_config, '$.proxyPassword', '$.totpSecret')
+WHERE json_valid(ssh_config)
+  AND (json_extract(ssh_config, '$.proxyPassword') IS NOT NULL OR json_extract(ssh_config, '$.totpSecret') IS NOT NULL);
+
+INSERT INTO schema_version (version, applied_at) VALUES (9, datetime('now'));
diff --git a/rust/core/src/storage.rs b/rust/core/src/storage.rs
index 0662dc5..406b9c5 100644
--- a/rust/core/src/storage.rs
+++ b/rust/core/src/storage.rs
@@ -17,6 +17,7 @@ const MIGRATIONS: &[(i64, &str)] = &[
     (6, include_str!("../migrations/006_irc_channel_state.sql")),
     (7, include_str!("../migrations/007_serial_protocol.sql")),
     (8, include_str!("../migrations/008_rdp_protocol.sql")),
+    (9, include_str!("../migrations/009_purge_legacy_secrets.sql")),
 ];
 
 const PROFILE_COLS: &str = "id, display_name, description, protocol, host, port, username,
@@ -118,23 +119,50 @@ fn scan_snippet(r: &Row) -> rusqlite::Result<Snippet> {
 
 impl Store {
     pub fn open(path: &Path) -> Result<Store> {
+        // Owner-only from the first byte (the data folder is 0700 too, but the file may be copied
+        // or backed up on its own).
+        #[cfg(unix)]
+        if !path.exists() {
+            use std::os::unix::fs::OpenOptionsExt;
+            std::fs::OpenOptions::new().write(true).create_new(true).mode(0o600).open(path).map_err(|e| format!("storage: failed to create database: {e}"))?;
+        }
         let db = Connection::open(path).map_err(|e| format!("storage: failed to open database: {e}"))?;
         db.busy_timeout(std::time::Duration::from_secs(5))?;
         db.pragma_update(None, "journal_mode", "WAL")?;
+        // Deleted rows (edited profiles, removed audit entries) are zeroed rather than left in
+        // free pages.
+        db.pragma_update(None, "secure_delete", "ON")?;
+        #[cfg(unix)]
+        for suffix in ["", "-wal", "-shm"] {
+            let mut p = path.as_os_str().to_owned();
+            p.push(suffix);
+            let _ = std::fs::set_permissions(&p, std::os::unix::fs::PermissionsExt::from_mode(0o600));
+        }
         let s = Store { db: Mutex::new(db) };
         s.migrate().map_err(|e| format!("storage: migration failed: {e}"))?;
         Ok(s)
     }
 
+    /// Applies pending migrations, each in its own transaction: several rebuild a table
+    /// (create new, copy, DROP old, rename), and a crash between the DROP and the rename used to
+    /// leave a database that failed to open on every later launch.
     fn migrate(&self) -> Result<()> {
-        let db = self.db.lock();
+        let mut db = self.db.lock();
         db.execute_batch("CREATE TABLE IF NOT EXISTS schema_version (version INTEGER PRIMARY KEY, applied_at TEXT NOT NULL)")?;
         let current: i64 = db.query_row("SELECT COALESCE(MAX(version), 0) FROM schema_version", [], |r| r.get(0))?;
         for (ver, sql) in MIGRATIONS {
             if *ver > current {
-                db.execute_batch(sql).map_err(|e| format!("failed to apply migration {ver:03}: {e}"))?;
+                let tx = db.transaction()?;
+                tx.execute_batch(sql).map_err(|e| format!("failed to apply migration {ver:03}: {e}"))?;
+                tx.commit()?;
             }
         }
+        if current < 9 && current > 0 {
+            // Migration 009 removed plaintext secrets; rewrite the file so their pages go too.
+            // In WAL mode the rewrite lands in the WAL; checkpoint it into the main file and
+            // truncate the WAL so neither keeps the old pages.
+            let _ = db.execute_batch("VACUUM; PRAGMA wal_checkpoint(TRUNCATE);");
+        }
         Ok(())
     }
 
@@ -561,6 +589,51 @@ mod tests {
         }
     }
 
+    #[test]
+    fn a_failed_migration_rolls_back_and_legacy_secrets_are_purged() {
+        let tmp = std::env::temp_dir().join(format!("nexus-mig-{}.db", std::process::id()));
+        let _ = std::fs::remove_file(&tmp);
+        let s = Store::open(&tmp).unwrap();
+        let mut p = Profile::new(crate::models::Protocol::Ssh);
+        p.id = "legacy".into();
+        p.display_name = "old".into();
+        p.host = "h".into();
+        s.create_profile(&p).unwrap();
+        {
+            // Put the database back at version 8 with a Go-era ssh_config carrying secrets.
+            let db = s.db.lock();
+            db.execute_batch(
+                "UPDATE profiles SET ssh_config = json_set(ssh_config, '$.proxyPassword', 'hunter2', '$.totpSecret', 'JBSWY3DP') WHERE id = 'legacy';
+                 DELETE FROM schema_version WHERE version = 9;",
+            )
+            .unwrap();
+        }
+        drop(s);
+        let s = Store::open(&tmp).unwrap();
+        let raw: String = s.db.lock().query_row("SELECT ssh_config FROM profiles WHERE id = 'legacy'", [], |r| r.get(0)).unwrap();
+        assert!(!raw.contains("hunter2") && !raw.contains("JBSWY3DP"), "{raw}");
+        for suffix in ["", "-wal"] {
+            let bytes = std::fs::read(format!("{}{suffix}", tmp.display())).unwrap_or_default();
+            assert!(!String::from_utf8_lossy(&bytes).contains("hunter2"), "old secret left in nexus.db{suffix}");
+        }
+        // A migration that fails part-way leaves nothing behind.
+        let mut db = s.db.lock();
+        let tx = db.transaction().unwrap();
+        assert!(tx.execute_batch("CREATE TABLE half (x); SELECT * FROM no_such_table;").is_err());
+        drop(tx);
+        assert!(db.prepare("SELECT * FROM half").is_err(), "rolled back");
+        drop(db);
+        #[cfg(unix)]
+        {
+            use std::os::unix::fs::PermissionsExt;
+            assert_eq!(std::fs::metadata(&tmp).unwrap().permissions().mode() & 0o777, 0o600);
+        }
+        drop(s);
+        for suffix in ["", "-wal", "-shm"] {
+            let _ = std::fs::remove_file(format!("{}{suffix}", tmp.display()));
+        }
+    }
+
     #[test]
     fn known_hosts_are_looked_up_per_key_type() {
         let tmp = std::env::temp_dir().join(format!("nexus-kh-{}.db", std::process::id()));
diff --git a/rust/core/src/validation.rs b/rust/core/src/validation.rs
index 3178ef5..77f2171 100644
--- a/rust/core/src/validation.rs
+++ b/rust/core/src/validation.rs
@@ -60,6 +60,10 @@ pub fn validate_profile(p: &Profile) -> Result<(), ValidationErrors> {
     let mut errs = ValidationErrors::default();
     if p.id.trim().is_empty() {
         errs.add("id", "profile ID must not be empty");
+    } else if p.id.len() > 64 || !p.id.chars().all(|c| c.is_ascii_alphanumeric() || matches!(c, '-' | '_' | '.')) {
+        // Ids name keychain/vault entries (`profile:<id>:<kind>`): a crafted id containing `:`
+        // could shadow or purge another profile's credentials.
+        errs.add("id", "profile ID may only contain letters, digits, '-', '_' and '.'");
     }
     if p.display_name.trim().is_empty() {
         errs.add("displayName", "display name must not be empty");
@@ -155,6 +159,12 @@ pub fn validate_host(host: &str) -> Result<(), ValidationError> {
     if h.contains([' ', '\t', '\n', '\r']) {
         return err("host", "host must not contain whitespace");
     }
+    if h.chars().any(is_control) {
+        return err("host", "host must not contain control characters");
+    }
+    if h.len() > 253 {
+        return err("host", "host is too long");
+    }
     if h.contains("://") {
         return err("host", "host must not include a URI scheme");
     }
@@ -206,8 +216,8 @@ pub fn validate_ssh_config(cfg: &SshConfig) -> Result<(), ValidationErrors> {
     }
     for (i, jh) in cfg.jump_hosts.iter().enumerate() {
         let prefix = format!("ssh.jumpHosts[{i}]");
-        if jh.host.trim().is_empty() {
-            errs.add(format!("{prefix}.host"), "jump host address must not be empty");
+        if let Err(e) = validate_host(&jh.host) {
+            errs.add(format!("{prefix}.host"), format!("jump host: {}", e.message));
         }
         if !(1..=65535).contains(&jh.port) {
             errs.add(format!("{prefix}.port"), "jump host port must be between 1 and 65535");
@@ -224,8 +234,13 @@ pub fn validate_ssh_config(cfg: &SshConfig) -> Result<(), ValidationErrors> {
         if !(1..=65535).contains(&pf.dest_port) {
             errs.add(format!("{prefix}.destPort"), "destination port must be between 1 and 65535");
         }
-        if pf.dest_host.trim().is_empty() {
-            errs.add(format!("{prefix}.destHost"), "destination host must not be empty");
+        if let Err(e) = validate_host(&pf.dest_host) {
+            errs.add(format!("{prefix}.destHost"), format!("destination: {}", e.message));
+        }
+        if !pf.bind_host.trim().is_empty()
+            && let Err(e) = validate_host(&pf.bind_host)
+        {
+            errs.add(format!("{prefix}.bindHost"), format!("bind address: {}", e.message));
         }
     }
     errs.into_result()
@@ -626,4 +641,21 @@ mod tests {
             assert!(validate_irc_config(&c).is_err(), "{rooms:?}");
         }
     }
+
+    #[test]
+    fn hosts_and_ids_reject_control_characters_and_separators() {
+        assert!(validate_host("a\0b").is_err() && validate_host("a\x1bb").is_err());
+        assert!(validate_host(&"a".repeat(254)).is_err() && validate_host("db.example.com").is_ok() && validate_host("::1").is_ok());
+        let mut p = Profile::new(Protocol::Ssh);
+        p.display_name = "x".into();
+        p.host = "h".into();
+        p.username = "u".into();
+        assert!(validate_profile(&p).is_ok(), "a generated id is valid");
+        for bad in ["victim:password", "../x", "a b", &"a".repeat(65)] {
+            p.id = bad.into();
+            assert!(validate_profile(&p).is_err(), "{bad:?}");
+        }
+        p.id = "rdp-test_1.a".into();
+        assert!(validate_profile(&p).is_ok());
+    }
 }