I am relaying a privacy issue for Bitcoin Core that was [reported on r/Bitcoin](https://reddit.com/r/Bitcoin/comments/klk2wh) (Reddit).

The [message](https://pastebin.com/raw/ptFQityt) was:

- _Using coin control_
- _Custom change address_

_When one clicks the increase transaction fee button, it adds another input rather than increasing the fee by reducing the change output. Major privacy leak since you have no control of the input used._

From that it sounds like the observed behavior is that the replacement transaction includes an additional UTXO that was not chosen by the user, even though the transaction was composed as a Coin Control transaction.

So I'm assuming the expected behavior would be for Bitcoin Core to remember that this OUTPUT was actually a Custom Change Address and to then lower the amount of that OUTPUT by the amount needed for the fee bump.

And, now that I am thinking of this, isn't there the expectation that if my initial transaction was done using Coin Control, and then if my fee bump (RBF) needs another UTXO input to cover the increase in fee, that Coin Selection for that will occur (regardless of whether or not the change address was a Custom Change Address)?  
constexpr int RANDOM_CHANGE_POSITION = -1;
    auto res = CreateTransaction(wallet, recipients, RANDOM_CHANGE_POSITION, coin_control, true);
    if (!res) {
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, util::ErrorString(res).original);
    }
    const CTransactionRef& tx = res->tx;
    wallet.CommitTransaction(tx, std::move(map_value), {});
    if (verbose) {
        UniValue entry(UniValue::VOBJ);
        entry.pushKV("txid", tx->GetHash().GetHex());
        entry.pushKV("fee_reason", StringForFeeReason(res->fee_calc.reason));
        return entry;
    }
    return tx->GetHash().GetHex();
}
/**
 * Update coin control with fee estimation based on the given parameters
 *
 * @param[in]     wallet            Wallet reference
 * @param[in,out] cc                Coin control to be updated
 * @param[in]     conf_target       UniValue integer; confirmation target in blocks, values between 1 and 1008 are valid per policy/fees.h;
 * @param[in]     estimate_mode     UniValue string; fee estimation mode, valid values are "unset", "economical" or "conservative";
 * @param[in]     fee_rate          UniValue real; fee rate in sat/vB;
 *                                      if present, both conf_target and estimate_mode must either be null, or "unset"
 * @param[in]     override_min_fee  bool; whether to set fOverrideFeeRate to true to disable minimum fee rate checks and instead
 *                                      verify only that fee_rate is greater than 0
 * @throws a JSONRPCError if conf_target, estimate_mode, or fee_rate contain invalid values or are in conflict
 */
static void SetFeeEstimateMode(const CWallet& wallet, CCoinControl& cc, const UniValue& conf_target, const UniValue& estimate_mode, const UniValue& fee_rate, bool override_min_fee)