The current version in the repository is 4.05.0 (released on Jul 12, 2017),
please update ocaml to the current upstream version 4.06.1 (released on Feb 16,
2018).

Starting with version 4.06.0 a bug has been fixed in 4.05.0 that could also be
considered security related. Excerpt from the change log:

https://github.com/ocaml/ocaml/blob/81dc8e8fcf923baa5e5208f9bc4228930c7c3d56/Changes

OCaml 4.06.0 (3 Nov 2017):
...
MPR#7640, GPR#1414: reimplementation of Unix.execvpe to fix issues with the
4.05 implementation.  The main issue is that the current directory was always
searched (last), even if the current directory is not listed in the PATH.


(I'm sorry if this is not the correct category for this bug, after a few
minutes looking around I didn't find it entirely clear where to submit update
request type bugs for packages. As it could be considered somewhat security
related, I submitted it here. Thanks.)