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# Missing rent cleanup The piggy program is designed so that only the PDA derived from the caller can withdraw SOL after some time. But there is a bug in this program. Find the bug and take SOL from the PDA. # Task 1 - Write your exploit Write your exploit inside [`test`](https://github.com/Cyfrin/solana-course/blob/main/apps/ctf/rent/exercise/tests/test.rs). # Build ```shell cargo build-sbf ``` # Test Your exploit is successful if the test passes. ```shell cargo test -- --nocapture ```

Missing rent cleanup

The piggy program is designed so that only the PDA derived from the caller can withdraw SOL after some time.

But there is a bug in this program. Find the bug and take SOL from the PDA.

Task 1 - Write your exploit

Write your exploit inside test.

Build

cargo build-sbf

Test

Your exploit is successful if the test passes.

cargo test -- --nocapture

Missing Rent Cleanup

A tactical challenge to Missing Rent Cleanup - Analyze a vulnerable piggy bank contract to uncover a critical bug in how account rent is managed. Develop a Rust exploit to bypass PDA restrictions and successfully extract the locked SOL.

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Course Overview

About the course

What you'll learn

Native Rust & Anchor framework

PDAs, CPIs, and SPL Tokens

DeFi builds: oracles, auctions, AMMs

Course Description

Meet your instructors

Tasuku Nakamura

Founder at smartcontract.engineer

Smart contract engineer and educator.

Last updated on January 12, 2026

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Rust Developer

Solana

Section 1: Course Intro

Duration: 8min

Section 2: Core Concepts

Duration: 23min

Section 3: Hello Program

Duration: 4min

Section 4: Oracle

Duration: 2min

Section 5: Piggy Bank

Duration: 4min

Section 6: Dutch Auction

Duration: 11min

Section 7: AMM

Duration: 4min

Section 8: CPI IDL

Duration: 0min

Section 9: Common Bugs

Duration: 0min

1. Missing Signer Check

A security-focused challenge to Missing Signer Checks - Uncover a critical vulnerability in an oracle program that neglects to verify transaction signatures. Write a Rust exploit to bypass ownership controls and update on-chain price data without valid authorization. Reading Time: 0min

2. Missing Authorization Check

A tactical challenge to Missing Authorization Checks - Detect and leverage a critical security oversight where an oracle program fails to validate transaction signers. Construct a Rust-based exploit to bypass ownership restrictions and manipulate on-chain price feeds without permission. Reading Time: 0min

3. Missing Pda Check

A tactical challenge to Missing PDA Check - Audit a vulnerable piggy bank smart contract to uncover a critical flaw in address verification. Develop a Rust-based exploit to bypass the intended logic and successfully drain SOL from an insecure Program Derived Address. Reading Time: 0min

4. Missing Rent Cleanup

Give us feedback!

Course Overview

About the course

What you'll learn

Native Rust & Anchor framework

PDAs, CPIs, and SPL Tokens

DeFi builds: oracles, auctions, AMMs

Course Description

Meet your instructors

Tasuku Nakamura

Founder at smartcontract.engineer

Smart contract engineer and educator.

Last updated on January 12, 2026