Short answer. It depends on who bought it. Philippine law normally lets a debtor extinguish a purchased, disputed credit by paying only the price the buyer paid. Article 1635 removes that discount in specific situations, including a sale to someone paid with the credit itself, so the amount owed can be the full credit, not the auction price.
What the law says
From the provisions of the preceding article shall be excepted the assignments or sales made: (1) To a co-heir or co-owner of the right assigned; (2) To a creditor in payment of his credit; (3) To the possessor of a tenement or piece of land which is subject to the right in litigation assigned.
Civil Code, Article 1635 — Exceptions to Redemption of a Litigated Credit. Read the full provision →
The general rule this article carves an exception into
Philippine law lets a debtor whose disputed credit is sold to a stranger step in and end the debt by paying the buyer only what the buyer actually paid for it, plus related costs — a protection against a third party buying someone else's litigation cheaply and then collecting the full amount from the debtor. Article 1635 lists the situations where that discount does not apply.
When the discount does not apply
The three exceptions share a common thread: the buyer is not really a stranger cashing in on someone else's dispute. A sale to a co-heir or co-owner of the credit is really one owner consolidating what was already partly theirs. A sale to a creditor being paid with the credit itself, instead of cash, is not a purchase for profit at a discount — it is how the seller settled what they owed. A sale to the possessor of the very property the credit concerns is the person already most connected to the dispute. In each case, the law sees no discount to police.
What this means if your debt was sold at auction
If the buyer at the judicial auction fits one of these three descriptions — most plausibly the second, where the sale was a way of paying a debt the original creditor owed the buyer — the discounted redemption right does not apply, and you would owe the new holder the credit as it actually stands, not the price paid at auction. If none of the three applies, the general rule may still let you extinguish the debt at the price paid.
Why this needs your specific facts
Which category a sale falls into turns on how the buyer acquired the credit and their relationship to the original creditor — details that vary case by case and are not something a general answer can determine for you. Have a lawyer review the auction documents and the assignment itself before you pay anyone, so you are not overpaying a buyer who was never entitled to the full amount, or underpaying one who was.