The Tribune Co. bankruptcy keeps producing juicy legal storylines: a bench smackdown of Sidley Austin’s proposed $1,100 per hour rates, a debate over expensive fee examiners, a cameo from Warren Beatty and, most central to the case, a possible lawsuit against the banks that engineered the leveraged buyout that ruined Tribune.

Now, that last issue has produced a new twist: possible sanctions against a bondholder after its law firm, Brown Rudnick, mistakenly included confidential papers in a public filing, court records show. Martin Siegel, a Brown Rudnick partner, says the mistake was “inadvertent,” and that the firm has pulled the offending material from its filing. But Siegel says his firm will challenge the motion, filed by JPMorgan Chase and its lawyers at Davis Polk & Wardwell, to sanction Brown Rudnick’s client (a bondholder called Wilmington Trust Co.). Possible sanctions include a ban on Brown Rudnick’s client from accessing a trove of critical confidential documents, according to a source familiar with the matter.