According to CoinMeta, the Zcash Foundation announced seven security fixes for Zebra 7.0.0 before the upgrade of the NU7 mainnet, with the upgrade scheduled for around November 5th. Zebra 7.0.0 was released on October 22nd, and the latest announcement was a progress report before activation. The foundation described six security issues as potentially causing node synchronization delays, occupying verification resources, or leading to the disabling of honest nodes, while the seventh issue could potentially lead to the collapse of Zebrad. The foundation categorized five of the recommendations as high severity and two as medium severity. High-severity issues included two checkpoint synchronization failures, insufficient penalties for invalid transparent scripts, expensive signature calculations, and transaction checks that could occupy verification threads. The foundation stated that mainnet operators must upgrade before block 3,543,405; nodes that have upgraded will disconnect from peer nodes running the old version.