Oregon Revised Statutes Revenue and Taxation § 312.220

Any judgment for the sale of real property to the county, on foreclosure for delinquent taxes, is conclusive evidence of its regularity and validity in all collateral proceedings, except where the taxes have been paid or the property was not liable to assessment and taxation. The judgment is prima facie evidence that the taxes have not been paid and that the property was subject to taxation at the time it was assessed. The judgment shall estop all persons raising objections thereto, or to the title based thereon, which existed at or before the date of the judgment and could have been presented as an objection or defense to the application for the judgment.