Murderer Mark Bridger, who was jailed for killing five-year-old April Jones, has launched a legal bid, the girl's parents told The Sun.
Parents Coral and Paul Jones said police warned them of an initial hearing at the Court of Appeal next month, which the couple plan to attend.
It is not known whether the appeal is against his conviction or sentence.
Bridger, a father of six, snatched April near her home in Machynlleth, Wales, on October 1 last year.
The five-year-old's body has never been found.
The search engine block on obscene images of children protects potential victims and does not compromise free speech, David Cameron's child protection adviser has told Daybreak.
Claire Perry was defiant in her support for the block, which will prevent images of child sexual abuse and links to obscene content from being published.
She explained: "I have met the parents of Tia Sharp and April Jones and they were just bewildered that people could put terms into a computer and have images that are illegal in this country returned onto their laptops or their computers, with, in some cases, awful consequences."
Ms Perry admitted there was an "ideological battle" to keep the internet censorship-free, but was adamant a line in the sand had to be drawn when it came to obscene images of children.
Prosecutor Jonathan Sharp said: "The defendant saw him and walked directly up to him with the blade held between thumb and forefinger.
"He then slashed him down the face, causing a deep wound extending from temple to chin.
"He paused for a moment and looked Bridger directly in the eyes, in Bridger's own words 'as if to admire his work or show me who it was'."
The child killer also suffered a cut to his arm as he tried to defend himself.
Bridger needed more than 30 stitches to the face wound, which required surgery under general anaesthetic. He will be scarred for life.
Ferreira and other life prisoners had talked about attacking Bridger to make him reveal the whereabouts of April's body, police were told.
The premeditated attack happened three days after Bridger was allowed to associate with other prisoners.
Ferreira made a weapon out of a prison-issue razor with extra blades attached to the handle.
A life prisoner slashed child killer Mark Bridger from temple to chin, severing an artery, in an attempt to get him to reveal where April Jones's body was hidden, a court was told.
Convicted murderer and rapist Juvinal Ferreira attacked Bridger with a knife made from a razor at top security Wakefield Prison in July.
He was sentenced to a second life sentence at Leeds Crown Court and had five years added to his minimum term, meaning he will not be released before 2036.
The family of April Jones bid an emotional farewell to the five-year-old today, almost a year since the first anniversary of her murder.Read the full story ›
The family of April Jones said a final farewell as the town that shared their grief came to a standstill.
The tiny white coffin carrying her remains was borne through the streets of Machynlleth in a horse-drawn hearse as the community stood in silence or followed behind, all wearing pink in tribute to the schoolgirl.
Paul Davies reports:
Pink floral tributes were placed at the entrance of St Peter's Church by well-wishers, carrying heartfelt messages of sympathy for April Jones and her family.
One stated simply: "Fly high little angel, forever in our hearts, lots of love, Lorna, Boyd, Connie, Ella and Ewan."
Another pink bouquet carried the message: "In loving memory of April. From Nan and Grandad."
The Order of Service pictured a carefree and smiling April Jones on the beach wearing a bright orange top and shorts.
Her devastated mother sobbed audibly in grief as she walked slowly into the funeral service for her murdered daughter.
After the service, the funeral party left the church for a private burial.
Reverend Kathleen Rogers told the congregation: "We have come together to remember April in the presence of God. We have come to celebrate her short life and grieve together, to say goodbye.
"It's a bittersweet moment. Our hopes and dreams have changed because April has been taken from us.
"But you know, we come also with a sense of thanksgiving for the many ways that April touched our lives and those with whom she came into contact.
"For a five-year-old she touched a great many lives ... for Paul, Coral, Jazmin and Harley, April was and is extra special.
"But she touched us all and we think and feel differently because of the difference she made to us.
"Today, here in this place, she is linking us all together in grief. Yet, grief goes hand in hand with love.
"In whatever way we express our grief, it shows our love for April.
"And surely that is the most important thing for any human being of whatever age, simply to be loved."