Typically you will have the banks payoff the back taxes and unpaid HOA dues. You can doublecheck with your escrow company if you are in the middle of your purchase.
Good luck...short sales can take a long time and often don't close.
Property taxes are government liens, they are superior to ALL other liens, including deeds of trust (mortgage liens). If they go unpaid during a sale, they WILL be passed along to you - they go with the property, not the people. You need to make sure they are settled during your purchase, or count on paying them later.
Lenders know this, of course, so you could not actually finance this purchase without settling all unpaid taxes. No lien holder wants to be in a subordinate position to defaulted taxes. The county will demand payment on the fifth year and foreclose/auction the property if they are not paid.
You asked about risks regarding liens and I would suggest that you use an experienced title representative at the very least during your transaction. Lenders are NOT responsible for clearing title. That's your job...
Are you planning to finance this transaction? Lenders require title insurance and other processes that will benefit you. If you are not acquiring a loan, then use an experienced title/escrow agent and get title insurance. They will dig into county records and locate ALL claims to title. Your title policy, payable at closing, will protect you against anything they don't pick up.
Hope this helps... Let me know if I can clarify this in any way...