The ChangeLog lists the following changes since release 25~rc1:

• Fix documentation of MotdPhrase length, which actually is 126 characters: update sample configuration file as well as the man page. Thanks to shankari shankari@eecs.berkeley.edu. Closes #254.
• Implement new configuration option MaxPenaltyTime, which configures the maximum penalty time increase in seconds, per penalty event. Set to -1 for no limit (the default), 0 to disable penalties altogether. ngIRCd doesn't use penalty increases higher than 2 seconds during normal operation, so values higher than 1 rarely make sense. Disabling (or reducing) penalties can greatly speed up "make check" runs for example, see below, but are mostly a debugging feature and normally not meant to be used on production systems! Closes #249 and #251. Some example timings running "make check" from my macOS workstation:
  • MaxPenaltyTime not set: 4:41,79s
  • MaxPenaltyTime = 1: 3:14,71s
  • MaxPenaltyTime = 0: 25,46s
• Fix compilation without deprecated OpenSSL APIs. Thanks to Rosen Penev rosenp@gmail.com for the patch! Closes #252.
• Update Xcode project for latest Xcode version (10.0)
• Fix some compiler warnings of Apple Xcode/Clang
• Allow a 5th parameter in WEBIRC. Thanks to "ItsOnlyBinary". Closes #247.
• Update some more documentation files and source code comments.
• Platforms.txt: Add and update systems.

All changes of ngIRCd 25~rc1 are of course included as well :-) Most notably, citing the NEWS file:

• Only send TOPIC updates to a channel when the topic actually changed: This prevents the channel from becoming flooded by unecessary TOPIC update messages, that can happen when IRC services try to enforce a certain topic but which is already set (at least on the local server), for example. Therefore still forward it to all servers, but don't inform local clients (still update setter and timestamp information, though!).
• Update Xcode project for latest Xcode version (9.2). This includes adding missing and deleting obsolete file references.
• Handle user mode "C" ("Only users that share a channel are allowed to send messages") like user mode "b" ("block private messages and notices"): allow messages from servers, services, and IRC Operators, too. Change proposed by "wowaname" back in 2015 in #ngircd, thanks!
• Allow IRC Ops and remote servers to KILL service clients: such clients behave like regular users, therefore IRC operators and servers should be able to KILL them: for example to resolve nick collisions. Closes #242.