--- ### Liquidity Providers A natural question that arises from here is: **_Where do funds for the loan initial come from?_** The answer is a familiar one - `Liquidity Providers`! Much like we saw in `TSwap`, where a `Liquidity Provider` would deposit funds into a pool to earn fees, the same takes place with `flash loans`. A `Liquidity Provider` would deposit funds into a `flash loan` protocol, receiving some form of LP Token representative of their contribution. The `flash loan` protocol then accrues fees as people use `flash loans`, which increases the value of a `Liquidity Provider`'s representative allotment of the pool. 
Liquidity Providers
A natural question that arises from here is:
Where do funds for the loan initial come from?
The answer is a familiar one - Liquidity Providers!
Much like we saw in TSwap, where a Liquidity Provider would deposit funds into a pool to earn fees, the same takes place with flash loans.
A Liquidity Provider would deposit funds into a flash loan protocol, receiving some form of LP Token representative of their contribution. The flash loan protocol then accrues fees as people use flash loans, which increases the value of a Liquidity Provider's representative allotment of the pool.
Liquidity Providers
Overview - Flash Loans & Liquidity Providers.' Emphasis on liquidity providers, flash loans, transaction fees, and benefits for depositors.
1. Introduction
Learn to find bugs without code inspection. Topics include fuzzing, AMMs, constant product formula, Uniswap/Curve Finance concepts, and more. Duration: 5min
2. Phase 1: Scoping
Beginning our scoping phase of TSwap a fork of Uniswap V1. Duration: 9min
3. Primer On This Review
Learn about protocol invariance without code. Study DEXs & DeFi Security Reviews. Explore TSWAP Protocol Docs w/ Diagrams & Videos. Duration: 2min
4. What is a DEX?
Decentralized exchanges explained through Uniswap and TSwap Duration: 3min
5. What is an AMM?
We're walked through what an AMM is and how it works in DeFi. Duration: 10min
6. Liquidity Providers
An explanation on liquidity providers and the sources of AMM fees for traders. Duration: 11min
7. How AMMs Work
Patrick further details AMMs and how they function in this quick review on How AMMs Work. Duration: 5min
8. TSwap Recon Continued
TSwap - Create New Pools, Swap Tokens via Multiple Pools, Liquidity Providers. Duration: 3min
9. Invariant & Properties Introduction
In-depth explanation of blockchain protocol invariants and fuzz testing. Examples from ERC-20 & ERC-721 tokens. Duration: 3min
10. Stateful And Stateless Fuzzing
Patrick details the differences between stateful and stateless fuzz testing and how each can be used to break protocol invariants. Duration: 10min
11. Stateless And Stateful Fuzzing Practice
Patrick emphasizes the importance of practice to master stateful and stateless fuzz testing. Duration: 5min
12. Stateless Fuzzing
Patrick walks through stateless fuzzing to catch an invariant break in TSwap! Duration: 9min
13. Where Stateless Fuzzing Fails
Patrick walks through some testing failures and how Foundry can be configured to achieve better results. Duration: 11min
14. Fuzzing Where Method 1 Fails
Introduction to different methods of fuzzing when we have no luck with Method 1. Duration: 18min
15. Stateful Fuzzing Method 2
A second approach to stateful fuzzing by Patrick. Duration: 14min
16. Debugging Fuzz Sequences
Uncover a broken invariant and debug the output sequence of our fuzz testing in this TSwap lesson. Duration: 7min
17. Fuzzing Recap
Stateful/Stateless Fuzzing, Handler Method Importance, ERC20 Exploit, TSWAP Testing & Bugs. Duration: 2min
18. Weird Erc20s
Patrick discusses various ERC20 quirks that can affect a protocol's security including missing return values and fee-on-transfer tokens. Duration: 4min
19. Writing Stateful Fuzz Test Suite
Stateful Fuzzing & Manual Review for TSWAP Bugs Duration: 1min
20. Constant Product Formula Explained
Explore the constant product formula and test it's implementation in TSwap through Fuzz and Unit testing. Duration: 9min
21. Invariant.t.sol
Patrick walks us through the invariant testing we perform on TSwap in invariant.t.sol. Duration: 17min
22. Handler.t.sol
Implementing the deposit function within our testing handler. Duration: 18min
23. Handler Swap Function
Implementing the swap function within our testing handler. Duration: 12min
24. Final Invariant And Tweaks
Comparing Deltas in Handler Test - Quick Guide. Demonstrates how to set up and run an assertion test for deltas in a handler. Duration: 3min
25. Debugging The Fuzzer
Debug Solidity Test Failures with Foundry Duration: 8min
26. One Last Huzzah
Patrick explains how fuzz testing and formal verification methods can be used together to detect bugs in Solidity smart contracts. Duration: 10min
27. Notes On Invariants
Covers security tools like fuzzing, Echidna, and mutation/diff testing to detect issues stresses the importance of testing & learning from history. Duration: 4min
28. Recon: Manual Review Introduction
In this video, Patrick discusses the importance of manual codebase review along with tooling, specifically focusing on TSWAP pool. Duration: 2min
29. Slither
Patrick runs through using Slither on the TSwap repo. Duration: 2min
30. Aderyn
Using Cyfrin's Aderyn to find some non-critical bugs in TSwap! Duration: 2min
31. PoolFactory.sol
In this video, Patrick reviews PoolFactory.sol for TSwap liquidity pools, covering structure, functions, variables, bugs, and best practices. Duration: 6min
32. Manual Review: TSwapPool
Patrick discusses the security review of TSWAP pool in the context of Uniswap V1, He highlights a swap counting bug that breaks protocol invariants Duration: 3min
33. Using The Compiler As Static Analysis Tool
Importance is placed on addressing compiler warnings for potential issues and how they can help us in an audit scenario. Duration: 6min
34. Add Liquidity
Performing a manual review of the addLiquidity function and assessing risks found within! Duration: 8min
35. Remove Liquidity
Withdrawing Liquidity: Burning LP tokens to exchange for underlying money, parameters explained. Duration: 8min
36. swapExactInput
Understanding Swap Exact Input/Output & Protocol Checks in DeFi Duration: 6min
37. swapExactOutput
swapExactOutput lacks slippage protection for sudden price changes. Duration: 3min
38. sellPoolTokens
Sells pool tokens for WETH; business logic error: swap exact output instead of swap exact input. Duration: 2min
39. Checking The Last Few Functions
Patrick quickly skims the final few functions for vulnerabilities in TSwap. Duration: 2min
40. Phase 4: Reporting
Quick overview of reporting process - finding reports & appropriate tags. Multiple passes suggested for thoroughness. Duration: 5min
41. Reporting: Missing Deadline
TSWAP pool deposit function vulnerability. Deadline parameter accepted but unused, allowing MEV attacks during unfavourable market conditions. Medium impact. Duration: 4min
42. Reporting Continued
Patrick continues by showing how to report issues with examples and proofs to fix them. Duration: 10min
43. Reporting: No Slippage Protection
Slippage Protection Lacking in SwapExactOutput, Add Max Input for Safety. Patrick elaborates with a Proof-Of-Concept Scenario. Duration: 8min
44. Reporting: sellPoolTokens
Patrick highlights flawed SellPool tokens calculation. Recommends using swapExactInput & adding a MinWethToReceive w/Deadline to prevent exploitation. Duration: 4min
45. Reporting: Invariant Break & PoC
In this video, Patrick explains how to create a unit test that replicates a sequence found using fuzz testing to break an invariant. Duration: 9min
46. Reporting: Weird Erc20
Uniswap V1, TSWAP pool issues, breaks protocol invariance. Explore, and report weird ERC20s, DeFi vulnerabilities. Duration: 4min
47. Creating Pdf For Your Portfolio
Creating a PDF of your audit report to add to your GitHub portfolio! Show case your achievements! Duration: 4min
48. Recap
Recap things covered in this section. Common issues in DeFi: liquidity, price manipulation, governance attacks. Duration: 8min
49. Exercises
Learn smart contract security testing by coding a fuzz test, discover reentrancy attacks, share insights on Twitter. Upcoming sections explained. Duration: 3min