Affects Version/s: 2.6.3, 2.7.0
Fix Version/s: 2.8.0
It seems that e.g. 'sss' and 'ssss' (or 'S' and 'INS' and similar) are in some manner the same rooms for Spark. If those two rooms are opened and someone sends a message into one of them, then Spark will show this message in both rooms. If you close one of them and reopen, then its history will be posted in both rooms.
Updated path to reproduce:
1) create two rooms in Admin Console with jids and names: RMC and SRMC.
2) in Spark client A open SRMC rooms
3) in Spark client B open RMC and SRMC rooms
4) in Spark client C (or any other client than Spark) open RMC room
5) client A sends a message to room SRMC
6) client B receives that message in both SRMC and RMC rooms (should be only in SRMC)
7) client C doesn't see anything in RMC room
When client B closes both rooms and opens RMC room only, he sees no messages as it should be, but if he then opens SRMC also, then RMC gets that message from SRMC in the history. It is like Spark is pulling history for a room from the server and then pushes it too all the rooms with a similar ending of the name.