The vulnerability of function selector clashing (due to only a 4 bytes selector domain) exists in any contract.

In ZepplinOS, the community is able to deploy and propose upgrades to contract which the community may accept after a voting period. A malicious community member could upgrade to a deployed implementation that attacks users knowing that a naive community may accept it (not fully checking for selector clashes). This is the key difference compared with a typically SC which is deployed and audited/voted on by the dApp developers (not the community).

Would really appreciate you or Zeppelin confirming the above understanding of the issue. Thank you.