Every time you connect your wallet to a decentralized application — whether it is a decentralized exchange, a lending protocol, or a Telegram trading bot — you encounter a prompt asking for token approval. Most users click “approve” without fully understanding what they are agreeing to. The recent $640,000 Unibot exploit on October 31, 2023, serves as a stark reminder that understanding token approvals is not optional knowledge — it is essential survival skills for anyone participating in decentralized finance. With Bitcoin trading near $34,600 and the crypto market heating up, now is the time to learn these fundamentals before your next transaction.
The Basics
A token approval is a permission you grant to a smart contract that allows it to spend a specific amount of a token on your behalf. Think of it like giving someone a limited power of attorney over your bank account — they can withdraw funds up to the amount you specified, but no more. In the Ethereum ecosystem, this permission is implemented through the ERC-20 token standard’s approve() and allowance() functions.
When you want to swap tokens on Uniswap, for example, you first need to approve the Uniswap smart contract to spend your tokens. Only after this approval can you execute the swap. This two-step process exists for security reasons — it prevents any contract from arbitrarily taking your tokens without your explicit consent.
The problem arises when approvals are either too generous or granted to untrustworthy contracts. Many DeFi interfaces default to requesting unlimited approvals, meaning you are allowing the contract to spend your entire balance of that token. While convenient — you do not need to re-approve for future transactions — this creates significant risk if the contract is ever compromised.
Why It Matters
The Unibot exploit perfectly illustrates why token approvals matter. Unibot’s users had previously approved the trading bot’s router contract to spend their tokens. When a vulnerability was discovered in the newly deployed router — just one day after its launch — the attacker was able to use the transferFrom() function to drain approved tokens directly from user wallets. The users’ private keys were never compromised. The exploit worked entirely through the permissions that users had voluntarily granted.
This means that even if you have the most secure wallet setup imaginable — hardware wallet, strong passwords, two-factor authentication — a single ill-considered token approval can result in total loss of the approved tokens. Security in DeFi is only as strong as its weakest link, and token approvals are frequently that weakest link.
Getting Started Guide
Managing your token approvals does not require technical expertise. Here is a practical guide anyone can follow. First, audit your existing approvals. Visit a token approval management tool such as Revoke.cash or Unrekt.net. Connect your wallet — the same way you would connect to any DeFi application — and the tool will display all active approvals across supported networks. You will likely be surprised by how many permissions you have accumulated over time.
Second, revoke unnecessary approvals. For each approval listed, ask yourself: “Do I still use this protocol?” If the answer is no, revoke the approval immediately. If the protocol is one you use frequently, consider whether the approval amount is reasonable. Unlimited approvals on small balances are less risky, but for large holdings, you should only approve the exact amount needed for each transaction.
Third, change your approval habits going forward. When interacting with DeFi protocols, look for options to set custom approval amounts instead of accepting the default unlimited approval. Some interfaces, like Uniswap, now offer the option to approve only the exact swap amount. Always prefer this option when available.
Fourth, use dedicated wallets for different activities. Maintain a “cold” wallet for long-term storage that never connects to any DeFi application. Use a separate “hot” wallet with limited funds for active trading and DeFi interactions. This way, even if a token approval is exploited, your main holdings remain safe.
Common Pitfalls
New users frequently make several avoidable mistakes with token approvals. The most common is blindly approving unlimited spending. Many DeFi interfaces present the unlimited approval as the default option because it reduces friction and gas fees, but this convenience comes at the cost of increased risk.
Another pitfall is never reviewing old approvals. Tokens you approved months or years ago for protocols you no longer use remain active until explicitly revoked. These dormant approvals are ticking time bombs — if any of these old protocols are compromised, your tokens are immediately at risk.
A third mistake is approving suspicious or unverified contracts. Before granting approval, check whether the contract is verified on Etherscan. If the contract source code is not publicly available, treat it as a red flag. The Unibot exploit targeted an unverified contract that had been deployed just one day before the attack.
Next Steps
Now that you understand the basics of token approvals, take immediate action. Visit Revoke.cash, connect your wallet, and review your current approvals. Revoke any that you do not actively need. Set a calendar reminder to repeat this review monthly. Going forward, always approve only the amount you need for each specific transaction, and use a dedicated hot wallet for all DeFi interactions. These simple habits will dramatically reduce your exposure to the kind of exploit that cost Unibot users $640,000 in a single day.
Disclaimer: This article is for educational purposes only and does not constitute financial advice. Always conduct your own research and consider consulting with a qualified professional before making financial decisions.
the Unibot exploit happened because the Telegram bot had unlimited approval on user wallets. $640K gone because nobody thought to cap the allowance
token approvals via erc20 approve and allowance still catch people off guard like unibot
the 640K unibot exploit is the perfect case study here. one token approval to a dodgy contract and your wallet is empty. i always set approval to exact amount needed, never unlimited
article says 34,600 btc price but the lesson applies at any price. approval = permission to drain. revoke after every single interaction
Yeong-ho L. i check my token approvals on revoke.cash weekly. found 47 open contracts from 2021 defi farming. most people have no idea whats still authorized on their wallet
ERC-2612 permit would solve most of this but adoption is still spotty. signing an approval costs gas, permit signatures are off chain and free. wallets should default to it
Prasad K. ERC-2612 permit is the actual fix. off-chain signatures cost zero gas and let you set exact amounts. wallets just need to adopt it
Prasad K. ERC-2612 permit is the cleanest fix but wallet adoption is still the bottleneck. MetaMask only added support recently and most L2 wallets still dont bother
found 47 open approvals on my wallet from 2021 farming. revoke.cash should be bookmarked by every single DeFi user, not optional
everyone should bookmark revoke.cash and use it after every DeFi session. unlimited approvals are how you wake up to an empty wallet
Amina K. revoke.cash is mandatory but the real fix is wallets showing active approvals by default. MetaMask has a balances tab but no approvals tab. thats a design failure
this. and stop approving unlimited amounts. most DEXs let you set exact amounts now, no reason to leave the door open
onchain_ghost exact amount approvals should be the default in every DEX. unlimited approval as a default setting is a design failure that cost users hundreds of millions
Jin Park exact amount approvals should be the ONLY default. unlimited is an advanced setting hidden behind 3 warnings. every DEX has the toggle, they just dont enable it
115081 100%. unlimited approvals as default is a UX failure that directly caused the Unibot 640k exploit. exact amount should be the only option with unlimited hidden behind advanced settings
allowance_zero ERC-2612 permit exists and solves this off-chain. zero gas for approvals, exact amounts only. wallets just need to adopt it but inertia is apparently stronger than security
Amina K. revoke.cash is essential but most people dont even know what approvals they have. should be built into every wallet UI as a default tab
built into wallet UI as a default tab is such an obvious feature. metaMask shows you your token balances but not your active approvals. its a massive UX failure
rads_check MetaMask adding an approvals tab would fix this overnight. crazy that in 2026 we still need third party tools to see what we authorized
the Unibot exploit at 640k happened because of infinite approvals on a trading bot. btc was at 34600 and people were getting wrecked by their own permissions
Ines T. 640K lost on Unibot because of infinite approvals on a trading bot. BTC at 34600 and people getting wrecked by their own permission settings
found 23 open approvals on my wallet from 2022 farming season last month. revoke.cash should be mandatory reading before anyone touches a DEX
the power of attorney analogy is perfect. explained this to my brother last week and that comparison finally made it click for him
the power of attorney analogy is good but even more accurate would be a blank check. unlimited approvals literally let the contract take everything, not just what you authorized for that specific swap
Emilia V. the blank check comparison is exactly right. stopped using unlimited approvals after the Unibot mess. costs slightly more gas but worth it
the blank check comparison from Emilia V. is spot on. unlimited approval literally lets the contract take everything you own, not just what you swapped