Office export is using way too much memory

I noticed a OOM on myxwiki.org caused by a huge org.apache.commons.io.output.ByteArrayOutputStream (550MB) produced during the office export. It's a local variable so the memory dump does not give much information about where exactly it's used but it shows that the office export is very bad at handling files (like putting them in memory instead of using temporary files).

For example OfficeConverter#convert return a map of files content as byte[] which is quite insane from memory point of view.