LNbits provides software for running Bitcoin Lightning wallets and payment applications, including merchant checkouts, tipping services and paywalls. Developer Ben Arc said in May that about 200,000 people run the software themselves.
LNbits first warned operators on Sunday to disable its Paywall extension while it investigated a potential vulnerability. Just over an hour later, the project urged users to shut down their LNbits servers immediately, citing a wave of attacks. It also took its own hosted installations offline.
The company has not yet detailed the exploit and how many were impacted by it. In an announcement accompanying the emergency patch, LNbits said the vulnerability affects all versions before 1.7.0 and puts funds at risk of theft.
It also warned that credentials exposed before upgrading could still give attackers access afterward, urging operators to reset wallet keys, replace funding-source credentials and treat secrets stored in LNbits settings as compromised and recommended moving to a fresh server if a compromise is suspected.
Cointelegraph reached out to Ben Arc and LNbits for comment.
One user, Kevin Ravensberg, said attackers exploited his LNbits instance, withdrawing about 2.3 million satoshis, or 0.023 Bitcoin, through newly created accounts before he could shut down the server.
The company said a separate report detailing the exploit would follow.