According to Foresight News, Bitcoin Core developer Luke Dashjr has revealed that Inscriptions is exploiting a vulnerability in the Bitcoin Core client to send spam messages to the blockchain. Since 2013, Bitcoin Core has allowed users to set extra data size limits when forwarding or mining transactions using the '-datacarriersize' parameter. Inscriptions bypasses this limit by disguising its data as program code.
Dashjr stated that the vulnerability was recently fixed in Bitcoin Knots v25.1. However, due to significant disruptions in his workflow at the end of last year, the fix took longer than usual, with v24 being completely skipped. The upcoming v26 version of Bitcoin Core still contains the vulnerability, and Dashjr can only hope that it will be finally fixed before next year's v27 release.