Mattel Sued Over 'Wicked' Dolls Porn Link Printing Error

Mattel's "Wicked" doll drama has just escalated ... we've learned the toy company has been sued over last month's X-rated misprint.

Here's the skinny ... Mattel issued a recall in November after accidentally putting a porn link on the back of its Elphaba and Glinda dolls to coincide with the release of the "Wicked" movie. The company responded by pulling the toys from shelves and issuing an apology for the NSFW error.

However, in a new court document obtained by TMZ, a South Carolina mother says Mattel didn't do enough ... launching a class action lawsuit against the maker of Barbie.

The mom claims she purchased a "Wicked" doll just before the recall for her minor daughter, who she says used an iPhone to look up the link listed on the packaging ... only to be exposed to "hardcore, full on nude pornographic images depicting actual intercourse."

The mom says she has evidence of this "inexcusable error" ... noting she and her daughter were left "horrified" by the material.

The plaintiff says Mattel did not offer a refund for the tainted toy and she believes she's incurred damages as a result. Specifically, she says she and her daughter suffered emotional distress from the mistake.

As the mom puts it ... Mattel failed to produce an age-appropriate product, which was advertised for users as young as 4, and she would have never purchased the doll had she known there was an X-rated link on the box.

We've reached out to Mattel for comment ... so far, no word back.