// CRITICAL: SignerCapability stored with 'store' ability allows extraction
struct ResourceAccountCap has key, store {
    signer_cap: account::SignerCapability,
}

// If anyone can get a reference to this struct, they can create a signer
// for the resource account and drain all its assets
public fun get_resource_signer(cap: &ResourceAccountCap): signer {
    account::create_signer_with_capability(&cap.signer_cap)
}

// SAFE: No public accessor, internal only
struct ResourceAccountCap has key {
    signer_cap: account::SignerCapability,
}

fun internal_get_signer() acquires ResourceAccountCap {
    let cap = borrow_global<ResourceAccountCap>(@resource_addr);
    let signer = account::create_signer_with_capability(&cap.signer_cap);
    // Use signer internally only
}

// VULNERABLE: Depositing without checking CoinStore registration
public fun distribute_rewards(recipients: &vector<address>) {
    let i = 0;
    while (i < vector::length(recipients)) {
        let addr = *vector::borrow(recipients, i);
        // ABORTS if addr doesn't have CoinStore<RewardToken> registered!
        coin::deposit(addr, reward_coins);
        i = i + 1;
    };
}

// SAFE: Check registration first
public fun distribute_rewards(recipients: &vector<address>) {
    let i = 0;
    while (i < vector::length(recipients)) {
        let addr = *vector::borrow(recipients, i);
        if (coin::is_account_registered<RewardToken>(addr)) {
            coin::deposit(addr, reward_coins);
        } else {
            // Handle: skip, queue for later, or register for them
        };
        i = i + 1;
    };
}