BIP 360 has been under discussion for quite some time, but it was published in the BIP repository today.
This proposal seems relatively simple compared to some of the other quantum resistance proposals out there. BIP 360 proposes a new output type called pay-to-merkle-root (P2MR). This output type is pretty much the same as taproot outputs, except this output doesn't expose its public key and is therefore safe from long exposure quantum attacks.
The BIP has a nice explanation of what a long exposure quantum attack is:
For clarity, this proposal specifically mitigates the risk of long exposure attacks on outputs that support tapscript and script trees. While some other Bitcoin output types, such as P2SH, are safe against long exposure attacks, taproot is not and taproot is the only currently activated output type that supports tapscript and script trees.
A long exposure attack is an attack performed on exposed blockchain data, such as exposed public keys, or the scripts of spent outputs. These are likely to be the earliest quantum attacks made possible on Bitcoin, because attackers will have ample time — as much time as vulnerable keys are exposed — to carry out quantum key recovery.
Short exposure attacks, however, require faster quantum computers, because they must occur within the relatively short time that a transaction is unconfirmed in the mempool.
Bitcoin outputs are generally vulnerable to short exposure attacks, as most Bitcoin transactions require revealing the associated public key when spending. Full protection of outputs from short exposure attacks may require the use of post-quantum signature schemes.
Since long exposure attacks on public keys are likely to be the first quantum-enabled threat to Bitcoin, we propose a script tree output that is resistant to long exposure attacks as a first step in hardening Bitcoin against the potential threat of quantum computers.
@cryptoquick, one of the BIP's co-authors, has made a nice website where you can learn more about it: https://bip360.org/