This is the whitepaper for the lightning network before it all got built.
https://lightning.network/lightning-network-paper.pdf

Under section 9.6, it states:

"9.6 Inability to Make Necessary Soft-Forks

Changes are necessary to bitcoin, such as the malleability soft-fork. Additionally, if this system becomes popular, it will be necessary for the system to securely transact with many users and some kind of structure like a blockheight timestop will be desirable. This system assumes such changes to enable Lightning Network to exist entirely, as well as soft-forks ensuring the security is robust against attackers will occur. While the system may continue to operate with only some time lock and malleability soft-forks, there will be necessary soft-forks regarding systemic risks. Without proper community foresight, an inability to establish a timestop or similar function will allow systemic attacks to take place and may not be recognized as imperative until an attack actually occurs."

A read through of the entire whitepaper is recommended.