We allow the following file types to be attached to posts:
123, AAC, AI, AIFF, ART, ASF, ASX, AVI, BMP, BZ2, CSD, DB, DMG, DOC, DOCX, DRW, EML, FLAC, FLV, GIF, GZ, ICS, JPEG, JPG, LOG, LTZ, M4A, M4P, M4V, MDB, MDBX, MID, MIDI, MMV, MOV, MP3, MP4, MPG, MSG, ODP, ODS, ODT, OGG, PDF, PL, PNG, PPS, PPT, PPTX, PS, PSD, QT, RAM, RAR, RM, RTF, SIT, SITX, SQL, SWF, TIF, TIFF, TXT, VCF, VCS, WAV, WMA, WMV, WPD, WPS, XLS, XLSX, XML, ZIP
To attach a file to a post you would either drag and drop the file onto the editor body field or use the Insert > Image/video/file option and select a file by clicking Upload in the resulting popup:
Note that certain files will result in code content being generated in the post rather than an attachment. This is the case with many/most text-based files such as LOG, SQL, JS / JSON, TXT, XML.
If you have long files like LOG or TXT files, for example, or have a mix of files you need to attach, rather than attaching them individually so the post is very long, it might be better to ZIP those files together and upload/attach the ZIP or equivalent file to the post. If you would rather post a log file only post what is sufficient for troubleshooting so your post is not flagged for too many duplicate lines or repeated text.