So this is a BSC transaction, but it works exactly like ethereum (on the surface), and it's a swap on pancakeswap but it has the same ABI as uniswap.

I was looking at a bot that always buy when a new coin is listed then sell at 2x.

look at the input : https://bscscan.com/tx/0x0e49e1766b0583d4b2b698412693ffa188aa04798b2505ecd6c0436834164d1e

instead of having something like this in the input data:

Function: swapExactTokensForETHSupportingFeeOnTransferTokens(uint256 amountIn, uint256 amountOutMin, address[] path, address to, uint256 deadline)

MethodID: 0x791ac947
[0]:  00000000000000000000000000000000000000000000000068d4d80718d2c000
[1]:  0000000000000000000000000000000000000000000000000c1150eabf4efb72
[2]:  00000000000000000000000000000000000000000000000000000000000000a0
[3]:  00000000000000000000000071749af1e6a25ddf6f5c9711ea46fcbebfd1fb75
[4]:  00000000000000000000000000000000000000000000000000000000608da196
[5]:  0000000000000000000000000000000000000000000000000000000000000002
[6]:  000000000000000000000000375483cfa7fc18f6b455e005d835a8335fbdbb1f
[7]:  000000000000000000000000bb4cdb9cbd36b01bd1cbaebf2de08d9173bc095c

all you have is this :


why? how can this transaction be executed with only this in the input data?


  • It is just executing a function without paramerers, ie dummyFunction(). Without the source code there's not much we can do.
    – Ismael
    May 1, 2021 at 20:59

1 Answer 1


This transaction is not interacting with the exchange router itself, but with a custom contract (code not published).

Since the input is very short, it is likely calling a function without parameters on that custom contract, such as executePredefinedSwap() (just an example, the code is not published so we don't know what function is called).

The custom contract takes care of calling the appropriate functions on the exchange to do the swap.

  • Any idea of why it calls a contract that will then call the swap on pancakeswap? looks like a useless step to me... May 2, 2021 at 23:11
  • It seems that this is a sniping bot. So, he will fire a lot of transactions to get the first trade, but he only wants one transaction to succeed. If he did not use a smart contract as intermediary, he would have to call multiple swaps for that token on the exchange. He would then risk having multiple trades succeed instead of just one and buy way too much tokens. Just an hypothesis...
    – Undead8
    May 2, 2021 at 23:35

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