Add Revoke.cash card

Author: boundless-forest

cards/Revoke.Cash.md

@@ -0,0 +1,41 @@
+#show-card
+
+## What is Revoke.cash?
+
+[Revoke.cash](https://revoke.cash/) is a security tool in the [[Web3]] ecosystem that helps users manage and revoke token allowances (approvals) granted to different smart contracts and decentralized applications ([[DApp]]s). It provides a user-friendly interface for crypto users to monitor, control, and revoke permissions they have previously given to various protocols to spend their tokens.
+
+## Understanding Token Approvals
+
+In [[Ethereum]] and [[ERC-20]] compatible blockchains, when interacting with dApps and protocols like decentralized exchanges ([[DEX]]s), lending platforms, or [[NFT]] marketplaces, users often need to grant these applications permission to access and transfer tokens on their behalf. This is done through the `approve` function in the ERC-20 standard.
+
+These approvals come in two forms:
+- **Limited approvals**: Permission to spend up to a specific amount of tokens
+- **Unlimited approvals**: Permission to spend an infinite amount of tokens (most common)
+
+## Why Revoke.cash is Useful
+
+### Security Risks of Unlimited Approvals
+
+Many dApps request unlimited token approvals for user convenience, but this creates significant security risks:
+
+1. **Vulnerability to exploits**: If a dApp you've approved is hacked or has a vulnerability, attackers could drain all approved tokens
+2. **Smart contract risks**: Bugs or backdoors in approved contracts could lead to loss of funds
+3. **Forgotten approvals**: Users often forget which dApps they've granted permissions to over time
+
+### Benefits of Using Revoke.cash
+
+- **Visibility**: See all active token approvals across multiple chains in one dashboard
+- **Control**: Selectively revoke unnecessary or risky approvals
+- **Security**: Reduce attack surface by managing approval permissions
+- **Multi-chain support**: Works across Ethereum, Polygon, BSC, and many other EVM-compatible networks
+- **Risk reduction**: Minimize potential losses from smart contract vulnerabilities
+
+## Best Practices
+
+1. Regularly audit and revoke unnecessary token approvals
+2. Only approve the exact amount needed for a transaction when possible
+3. Revoke approvals immediately after completing transactions with a [[DApp]]
+4. Use [[hardware wallet]]s for additional security when managing approvals
+
+Revoke.cash has become an essential security tool for responsible Web3 users, helping to mitigate one of the most common yet overlooked security risks in the ecosystem.
+