OpenZeppelin Contracts's GovernorVotesQuorumFraction updates to quorum may affect past defeated proposals

[imhunterand]

Describe the bugs: 🐛

OpenZeppelin Contracts is a library for secure smart contract development. This issue concerns instances of Governor that use the module GovernorVotesQuorumFraction, a mechanism that determines quorum requirements as a percentage of the voting token's total supply. In affected instances, when a proposal is passed to lower the quorum requirements, past proposals may become executable if they had been defeated only due to lack of quorum, and the number of votes it received meets the new quorum requirement. Analysis of instances on chain found only one proposal that met this condition, and we are actively monitoring for new occurrences of this particular issue. This issue has been patched in v4.7.2. Users are advised to upgrade. Users unable to upgrade should consider avoiding lowering quorum requirements if a past proposal was defeated for lack of quorum.

Impact

This issue concerns instances of Governor that use the module GovernorVotesQuorumFraction, a mechanism that determines quorum requirements as a percentage of the voting token's total supply. In affected instances, when a proposal is passed to lower the quorum requirement, past proposals may become executable if they had been defeated only due to lack of quorum, and the number of votes it received meets the new quorum requirement.

Analysis of instances on chain found only one proposal that met this condition, and we are actively monitoring for new occurrences of this particular issue.

Recommended fix

Users unable to upgrade should consider avoiding lowering quorum requirements if a past proposal was defeated for lack of quorum. Request merge patch as 96879aec0421cbcb7440614be5675c3dbbcaee80

CVE-2022-31198 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N GHSA-xrc4-737v-9q75