14:09:50@test>db.char_test.find()
{ "_id" : "< >" }
14:09:52@test>^C
bye
./mongoexport --db test -c char_test
2018-08-24T14:10:06.798+1000    connected to: localhost
{"_id":"\u003c \u003e"}
2018-08-24T14:10:06.801+1000    exported 1 record

mongoexport does this even when using the output to file option.

mongoexport produces correct output when using CSV mode. That is, the problem only occurs in JSON mode.

The JSON specification says that all text between code points 0020 and 01FF are fine to be encoded as characters as is (except forward-slash and quotes) – not hex.

I tested with 4.0.0 but I'm told it happens in 3.6 as well.