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# Tutorial 25: Cross Chain Bridges Vulnerabilities

{% hint style="info" %}
[**Book an audit with Zokyo**](https://www.zokyo.io/)
{% endhint %}

#### Introduction

In the realm of blockchain networks, maintaining the security and consistency of the chain is paramount to ensuring the proper execution and integrity of smart contracts. One critical area of focus is addressing the risks associated with **chain reorganizations (re-orgs)**, which can impact the behavior of contracts and the outcomes of transactions. A **chain re-org** occurs when a blockchain network experiences a temporary fork, where different versions of the blockchain coexist until one is chosen as the canonical chain. This process can potentially invalidate previously confirmed transactions, leading to serious security issues for smart contracts.

Chain re-org vulnerabilities can affect a variety of decentralized applications (dApps) and protocols, especially those that rely on time-sensitive or transaction-dependent operations. Developers must carefully design contracts to handle these re-orgs effectively, ensuring that actions like token transfers, staking rewards, and governance decisions are not compromised. In this section, we will explore the security concerns associated with chain re-orgs, focusing on the risks they pose to smart contracts, including double-spending, incorrect transaction confirmations, and front-running. We will also cover best practices and mitigation strategies to reduce the impact of chain re-orgs on contract behavior, helping to safeguard user assets and maintain the integrity of blockchain applications.


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