Summary

When a vine is placed under a overhang with only two sides (top and N,S,W or E) surrounding it, it will eventually grow upwards into a block, destroying it in the process.

Reproduction

If this reproduction does not work, destroy all vines and retry from step 3

1. Use a fresh Spigot 1.8.6 instance with creative gamemode
2. Build a structure like this
3. Place a vine underneath a bedrock block, against the white wool wall
4. Execute the console/OP command /gamerule randomTickSpeed 1000
5. Wait and observe; the vine will eventually break the bedrock block above it, exposing red wool
6. Wait and observe further; the vine does not continue to break blocks above, as it is now surrounded by more than two sides

Testing

The above reproduction was tested on:

• Local server; vanilla 1.8.6 - no effect
• Live server; git-Spigot-ae40327-5084899 - reproducable
• Local server; git-Spigot-ae40327-8c14eb4 - reproducable
  • 1: Where the vine was placed
  • 2: Former location of bedrock block, overwritten by vine

Footnotes

• This issue was discovered and reported by a player on a server I admin
• This issue appears to have surfaced from an update within the last 7 days
• I have marked the bug as "Major" as it allows for the destruction of blocks such as bedrock or destruction of property, and is not caught as an event