xToken

The xToken protocol is the creation of xToken Labs, a group dedicated to experimentation and the decentralization of finance.

xToken creates tokenized strategies that maximize yield, eliminate mental overhead, and maintain liquidity.These strategies are represented by ERC-20 tokens called xAssets which are accessible to anyone in the world with an Ethereum wallet and an internet connection.

For more information about xToken, please visit https://xtoken.market/.

This bug bounty program is focused on their lending protocol smart contracts and is focused on preventing:

• Oracle failure or manipulation
• Economic financial attacks (including flash loan attacks)
• Susceptibility to Frontrunning
• Consensus failures
• Loss of user funds staked (principal) by freezing or theft

Rewards are distributed according to the impact of the vulnerability based on the Immunefi Vulnerability Severity Classification System. This is a simplified 5-level scale, with separate scales for websites/apps and smart contracts/blockchains, encompassing everything from consequence of exploitation to privilege required to likelihood of a successful exploit.

Critical/High severity smart contract bug reports must come with a PoC and a suggestion for a fix in order to be considered for a reward. Medium severity smart contract bug reports must include a suggestion for a fix to be considered for a reward.

Critical vulnerabilities are further capped at 10% of economic damage, with the main consideration being the funds affected in addition to PR and brand considerations, at the discretion of the team. However, there is a minimum of USD 30 000 for Critical bug reports.

Payouts are handled by the xToken team directly and are denominated in USD. Payouts are done in USDC.

The relevant xToken contracts can be found at https://github.com/xtokenmarket/xLend. However, only those in the Assets in Scope table are considered as in-scope of the bug bounty program.

Impacts in Scope

Only the following impacts are accepted within this bug bounty program. All other impacts are not considered as in-scope, even if they affect something in the assets in scope table.

• Smart Contracts/Blockchain
• Oracle failure or manipulation
• Economic financial attacks (including flash loan attacks)
• Susceptibility to Frontrunning
• Consensus failures
• Loss of user funds staked (principal) by freezing or theft

We are especially interested in receiving and rewarding vulnerabilities of the following types:

Smart Contracts and Blockchain

• Re-entrancy
• Logic errors
  • including user authentication errors
• Solidity/EVM details not considered
  • including integer over-/under-flow
  • including rounding errors
  • including unhandled exceptions
• Trusting trust/dependency vulnerabilities
  • including composability vulnerabilities
• Oracle failure/manipulation
• Novel governance attacks
• Economic/financial attacks
  • including flash loan attacks
• Congestion and scalability
  • including running out of gas
  • including block stuffing
  • including susceptibility to frontrunning
• Consensus failures
• Cryptography problems
  • Signature malleability
  • Susceptibility to replay attacks
  • Weak randomness
  • Weak encryption
• Susceptibility to block timestamp manipulation
• Missing access controls / unprotected internal or debugging interfaces

The following vulnerabilities are excluded from the rewards for this bug bounty program:

• Attacks that the reporter has already exploited themselves, leading to damage
• Attacks requiring access to leaked keys/credentials
• Attacks requiring access to privileged addresses (governance, strategist)

Smart Contracts and Blockchain

• Incorrect data supplied by third party oracles
  • Not to exclude oracle manipulation/flash loan attacks
• Basic economic governance attacks (e.g. 51% attack)
• Lack of liquidity
• Best practice critiques
• Sybil attacks

The following activities are prohibited by this bug bounty program:

• Any testing with mainnet or public testnet contracts; all testing should be done on private testnets
• Any testing with pricing oracles or third party smart contracts
• Attempting phishing or other social engineering attacks against our employees and/or customers
• Any testing with third party systems and applications (e.g. browser extensions) as well as websites (e.g. SSO providers, advertising networks)
• Any denial of service attacks
• Automated testing of services that generates significant amounts of traffic
• Public disclosure of an unpatched vulnerability in an embargoed bounty