Raw Therapee is one of the best RAW converters out there. Great detail extraction, little demosaicing artifacts, a broad set of tools, multi threaded operation... It simply has it all. But it also has Auto Levels turned on in Default profile. This can sometimes be scary, especially when you want to develop night shots.

All we need is a slightly underexposed image:

And what we get in RT is:

Looks broken, doesn't it? Note the highlight clipping that wasn't there in the original, the weird colors are much less of a problem. As Mateusz Ludwin suggested on pl.rec.foto.cyfrowa, it is so because RT equalizes brightness. According to him, everything should be fine after moving the brightness slider to zero:

As for me, this is not fine. In fact, it looks a bit worse than original...

But it's not a bug in Raw Therapee. It's just the simple algorithm isn't all that universal. For comparison, let's see what Digikam does to the very same image with Auto Levels:

It is better, but still not really good. The warm glare would look natural at sunset, but this is early afternoon! As this is not the holy grail, let's keep searching. Next one is the equalize filter from Digikam:

This is by far the most broken image. Colors are simply insane. But on the other hand, note that it also reveals the most detail in the highlights. The last thing tried, Digikam Automatic Exposure:

This one is completely satisfactionary. No artifacts, no sick colors, everything looks plain reasonable. But I still prefer the 15-seconds manual setting from Raw Therapee:

Finally, I'll repeat myself: none of these is in fact a bug. Those effects should look like that, as what they mean is something like "make all the colors histograms look like Gaussian distribution". But you should remember, that even if effects sometimes resemble what you want, it's never the same thing.