The Timelock contract has a cancellation function, and any entity with the Proposer role can cancel an item that is queued in the Timelock. However, the proper way to achieve this is to call the cancel function through the Governor contract, such that the Governor’s internal state will also be updated.
Cancelling the proposal in the Timelock (but not through the Governor) is something of an “undefined behavior.” Different flavors of the Governor will react differently in this situation. I believe, after a quick code dive, that the ENS Governor will do what many do in this situation, namely: if cancelled directly in the Timelock, the proposal status in the Governor will revert to “Succeeded”, allowing it to be queued in the Timelock again (with the clock reset).
Since anyone can requeue it, we have to assume the creator of the malicious proposal would do so. This means, the security council can’t juts cancel a malicious proposal. They have to cancel it over and over again.
Here’s the relevant code snippets to look at to verify this: