Evert Pot has posted an update to a previous post around Composer's vulnerability around installing the wrong packages in the case of a conflict. In this latest post he points out, however, that the bug is now fixed.
As an update to my previous post, the composer security problem now appears fixed. Good to see that a quick response was possible after all.
The original issue was caused by the "replace" functionality, allowing the possibility for an incorrect package to be installed instead of the one requested. Other posts with more details include this one from Pádraic Brady and Nils Adermann. if you're a Composer user, it's highly suggested you update your currently installed version (run a "composer self-update").