message in chat

[yordi21]

we were playing and suddenly in our chat a random message appeared stating this : "here might be a raillayer event in the future" we do not know how this was caused...we do have mod's but no mod regarding any change to train's
here's also a screenshot of it occuring

[posila]

That message doesn't exist in vanilla Factorio, it must be one of your mods or the scenario script.