Description:
Long story short... Our government provides weird xls files and...

Version: 6.2.8.2
Build ID: 1:6.2.8~rc2-0ubuntu0.18.04.1
CPU threads: 4; OS: Linux 4.15; UI render: default; VCL: kde5; 
Locale: lt-LT (lt_LT.UTF-8); UI-Language: en-US
Calc: threaded

libreoffice ./Desktop/dokumentas2.xml  (yeah I renamed file it should be .xls)
1:14: <?xml version = '1.0' encoding = 'utf-8'?>
                   ^
malformed_xml_error: Attribute must begin with 'name=..'. (ns='', name='version')

but with 
Version: 5.3.4.2 (x64)
Build ID: f82d347ccc0be322489bf7da61d7e4ad13fe2ff3
CPU Threads: 8; OS Version: Windows 6.1; UI Render: default; Layout Engine: new; 
Locale: lt-LT (lt_LT); Calc: group

same file opens just fine. I also tried 6.1 on linux

From my friend I heard that this regression happens regularly.



Steps to Reproduce:
1. Open file

Actual Results:
With new version nothing with old version it opens.

Expected Results:
Always opens


Reproducible: Always


User Profile Reset: No



Additional Info:
I edited out actual information directly from xml, and results are unchanged you still can open file with old libre.