Violet Fungi, renamed to Venus Flytraps in Rogue V5, have been fixed.
The idea behind this monster is that it sticks to its prey, exuding corrosive chemicals. It is supposed to damage the player whether it hits or misses. Every time it hits, the amount of damage it does increases by one point.
I know this is what the authors intended, because the Vade-Mecum mentions it. But somewhere through the years, the mechanism broke. I suspect it happened when the Roguelike Restoration Project reorganized monster data to fix some other problems with the code. The Flytrap ended up doing no damage when it hit.
Fixing the problem was relatively simple. You can read the technical details in the commit message. The games on the server were updated two weeks ago, and there will be new binaries in the download section in a few days.
Since I pushed the fix to the server, several players have died to Flytraps. I think this has made the game substantially harder. The broken monster was hardly ever a threat, and killing it gave a lot of experience. When Flytraps work properly, exploring their levels while wounded is risky.
Rogue's original developers thought the number of bugs was "probably infinite", but I've never yet found one that made the game easier when it was fixed. As you explore their slightly less buggy creation, watch out for the letter F.