diff --git a/contracts/claims-processor/src/lib.rs b/contracts/claims-processor/src/lib.rs
index df0deb6..5797672 100644
--- a/contracts/claims-processor/src/lib.rs
+++ b/contracts/claims-processor/src/lib.rs
@@ -496,6 +496,10 @@ impl ClaimsProcessor {
         if policy.policyholder != *claimant {
             panic_with_error!(env, Error::Unauthorized);
         }
+        // Guard: reject claims for cancelled policies (issue #731).
+        if policy.status == parashield_policy_engine::PolicyStatus::Cancelled {
+            panic_with_error!(env, Error::PolicyNotActive);
+        }
         if policy.status != parashield_policy_engine::PolicyStatus::Active {
             panic_with_error!(env, Error::PolicyNotActive);
         }
diff --git a/contracts/governance-dao/src/lib.rs b/contracts/governance-dao/src/lib.rs
index c5858f0..79623a7 100644
--- a/contracts/governance-dao/src/lib.rs
+++ b/contracts/governance-dao/src/lib.rs
@@ -324,11 +324,10 @@ impl GovernanceDao {
             panic_with_error!(&env, Error::TitleTooLong);
         }
         
-        // SECURITY FIX: Validate impact analysis length to prevent storage exhaustion.
-        // Limit to 4096 bytes — reasonable for a proposal description without enabling
-        // attacks that reserve huge storage or inflate transaction costs.
-        if impact_analysis.is_empty() {
-            panic_with_error!(&env, Error::InvalidInput);
+        // SECURITY FIX: Validate proposal description (impact_analysis) is not empty (issue #732).
+        // Enforce non-empty and minimum length to ensure informative proposals, bounded up to 4096 bytes.
+        if impact_analysis.is_empty() || impact_analysis.len() < 5 {
+            panic_with_error!(&env, Error::EmptyDescription);
         }
         if impact_analysis.len() > 4096 {
             panic_with_error!(&env, Error::InvalidInput);
@@ -1872,6 +1871,10 @@ impl GovernanceDao {
     ) {
         Self::require_admin(&env, &admin);
 
+        if description.is_empty() {
+            panic_with_error!(&env, Error::EmptyDescription);
+        }
+
         if env.storage().instance().has(&StorageKey::Template(name.clone())) {
             panic_with_error!(&env, Error::DuplicateTemplateName);
         }
diff --git a/contracts/policy-engine/src/lib.rs b/contracts/policy-engine/src/lib.rs
index bbdb973..b88abdb 100644
--- a/contracts/policy-engine/src/lib.rs
+++ b/contracts/policy-engine/src/lib.rs
@@ -218,6 +218,8 @@ impl PolicyEngine {
         if oracle_buf[0] != b'C' {
             panic_with_error!(&env, Error::InvalidAddress);
         }
+        // Reject zero address as oracle (issue #730)
+        Self::require_not_zero_address(&env, &oracle_address);
 
         let balance_res = env.try_invoke_contract::<i128, soroban_sdk::Error>(
             &usdc_token,
@@ -367,6 +369,8 @@ impl PolicyEngine {
         if oracle_buf[0] != b'C' {
             panic_with_error!(&env, Error::InvalidAddress);
         }
+        // Reject zero address as oracle (issue #730)
+        Self::require_not_zero_address(&env, &new_oracle);
 
         let change = PendingOracleChange {
             new_oracle: new_oracle.clone(),
@@ -2004,6 +2008,17 @@ impl PolicyEngine {
     }
 
     fn migrate_v2_to_v3(_env: &Env) {}
+
+    /// Require that an address is not the zero address (issue #730).
+    fn require_not_zero_address(env: &Env, address: &Address) {
+        let zero = Address::from_string(&soroban_sdk::String::from_str(
+            env,
+            "GAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAWHF",
+        ));
+        if *address == zero {
+            panic_with_error!(env, Error::InvalidAddress);
+        }
+    }
 }
 
 #[cfg(test)]
diff --git a/contracts/risk-pool/src/lib.rs b/contracts/risk-pool/src/lib.rs
index 756fd91..aba76fd 100644
--- a/contracts/risk-pool/src/lib.rs
+++ b/contracts/risk-pool/src/lib.rs
@@ -281,8 +281,8 @@ impl RiskPool {
         if env.storage().instance().has(&StorageKey::Initialized) {
             panic_with_error!(&env, Error::AlreadyInitialized);
         }
-        // An empty category would make the pool's accounting and LP NFT
-        // metadata ambiguous, so reject it up front (issue #520).
+        // Category name cannot be empty and must describe a valid risk category (issue #729, #520).
+        // Empty category names are rejected to prevent unnamed categories in the pool registry.
         if category == Symbol::new(&env, "") {
             panic_with_error!(&env, Error::InvalidCategory);
         }