'Dallas' Star Victoria Principal's Home Compromised by Trespassers

Victoria Principal's private home became an unwanted open house this week -- courtesy of a couple of alleged trespassers who claimed they saw the place was for sale online and were told they could take a tour ... this according to law enforcement.

Cops say officers were called to the "Dallas" star's Malibu property Monday after a man and woman were spotted by security on surveillance cameras breaking through a gate and wandering onto the grounds.

Our sources say Principal's security lost sight of the pair, which made them think they might've broken into the home -- so we're told the call was upgraded to a possible burglary.

When cops arrived, they found the couple ... and cops say their explanation to officers was that they thought the crib was for sale -- claiming they'd seen an ad for it online and thought they'd pay the place a visit in person for a closer look.

We're told they even showed cops something they said was proof of a conversation between the couple and an unknown person on Craigslist trying to sell the home ... even giving instructions on how to get in.