If you are talking about what I think you are,
Yes, I am talking about exactly that data patch.
As many mods are going to rely on the original game's files using these patches to fix a few of the remaining glitches is worth the install and the setup is very easy.
If you installed the windows version of OpenXcom via the .exe release (Not the standalone .zip) it should already have the 'Data Patch' included... I think.
Thing is that XPiratez comes prepackaged with OpenXcom, and I, following the instructions in the readme, copy the files from my Steam X-Com installation to "XPiratez\UFO" which, if I remember correctly, has only a text file saying which files to copy over into the directory. As far as I understand, the Data Patch files should go into that directory. Does it means that XPiratez doesn't comes prepackaged with the Data Patch? I guess it's up to Dioxine - he knows for sure if the data patch is needed or not.
Never heard of the data patch, works just fine with just the base xcom files.
That's the point - I'm playing since J15, if not earlier and I've learned about Data Patch only recently, which made me wondering what is it and what it does.
Does it fixes a certain bug where some tiles of a certain terrain sets turned into tree stumps? There's more on that on UFOpaedia - against, I can't post links just yet, but you can look up on UFOpaedia Known_Bugs>Mountain_Map and Explosions>Mile-High_Madness.
Of course not.
OpenXcom Extended doesn't come with any original data, same as OpenXcom.
The patch is recommended also when using OpenXcom Extended.
If you're using the Windows installer, there is an option to download and apply the patch automatically.
Otherwise you can apply it manually.
Thank you for an answer! I'll guess I'll apply Data Patch the next time I'll install the fresh version of XPiratez and see for myself.