Using LN is marginally less secure than using Bitcoin. It is possible to attempt to broadcast a settlement transaction that is not the most recent and that results in you receiving more than the current state of your LN channel. However if you do this then the LN channel counterparty will be able to broadcast a transaction that results in them receiving all of the funds held in the channel.
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That sounds quite interesting, got any more details on this? How is the attacked counterparty able to retaliate by receiving all the funds held in the channel? What information gets leaked by the attacking transaction that enables this defensive measure?
Each time the participants create a new "state" of the LN channel, they will exchange signed transactions that allows either party to close the channel, however the party that broadcast the transaction will only be spend the funds after (it depends on the LN channel, but the LN white-paper used 1000 as an example) confirmations. This is done by using an intermediary transaction that can only be redeemed (by the person who broadcast the original transaction) after 1000 confirmations.
The above process will take place every time a new "state" of the LN channel. In addition to the above process, each party will exchange transactions that allows the party that did not broadcast the closing transaction if the closing transaction is from the previous "state" of the LN channel to spend the bitcoin that would normally belong to the party that broadcast the stale closing transaction.
When signed closing transactions are exchanged when there is a new "state" to the LN channel, the transaction sent to each party is slightly different (they have a different txid) so that it is possible to tell which party broadcast the closing transaction.
I think this is a little confusing, however I believe if you read it twice, it should make sense. If something doesn't make sense or if you have questions, let me know and I will explain further.