--- title: "Devoured by Bots: How a Missing Parameter Enabled 100% MEV Leakage in a DeFi Zap Contract" url: https://daily.dev/posts/devoured-by-bots-how-a-missing-parameter-enabled-100-mev-leakage-in-a-defi-zap-contract-dpme1dmpm source_url: https://coinsbench.com/devoured-by-bots-how-a-missing-parameter-enabled-100-mev-leakage-in-a-defi-zap-contract-e5f9e835dad2 type: article source: "Coins Bench" published: 2026-05-24T21:27:17.594Z updated: 2026-05-24T21:27:42.905Z tags: ["smart-contracts", "defi"] reading_time: 5 upvotes: 1 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Devoured by Bots: How a Missing Parameter Enabled 100% MEV Leakage in a DeFi Zap Contract **[Coins Bench](https://daily.dev/sources/coinsbench)** · 5 min read · 1 upvotes · 0 comments ## Summary A smart contract audit finding reveals a critical vulnerability in a Uniswap v4-based DeFi Zap contract where missing slippage protection on an internal swap enabled 100% MEV leakage via sandwich attacks. The StableSwapZapIn contract protected the final LP token minting step but left the intermediate token swap completely unguarded by setting sqrtPriceLimitX96 to its absolute extreme. This allowed MEV bots to front-run user transactions, inflate token prices, and extract nearly all deposited value. The fix requires accepting a user-defined minTokenBOut parameter for every internal swap, not just the final liquidity provision step. Key takeaway: every AMM interaction in a multi-step contract must have explicit slippage limits. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [How $50 Million Disappeared in 30 Seconds: A Code-Level Autopsy](https://daily.dev/posts/how-50-million-disappeared-in-30-seconds-a-code-level-autopsy-xgrdfj0vs) · Coins Bench · 1 upvotes · 0 comments - [I Built a Flash Loan Bot When I Couldn’t Afford Dinner](https://daily.dev/posts/i-built-a-flash-loan-bot-when-i-couldn-t-afford-dinner-t9xe3y0th) · Coins Bench · 2 upvotes · 0 comments - [Designing Blockchain Systems: What Smart Contract Tutorials Don’t Tell You \(Part 2\)](https://daily.dev/posts/designing-blockchain-systems-what-smart-contract-tutorials-don-t-tell-you-part-2--flggbflgg) · Coins Bench · 1 upvotes · 0 comments --- Tags: [#smart-contracts](https://daily.dev/tags/smart-contracts), [#defi](https://daily.dev/tags/defi) [View this post on daily.dev](https://daily.dev/posts/devoured-by-bots-how-a-missing-parameter-enabled-100-mev-leakage-in-a-defi-zap-contract-dpme1dmpm)