A sturdy rebuttal on Friday by Credit Corp of "an anonymous report" on the company provided only modest defence, in a trading context, as the firm's shares fell nearly 20 per cent, before rebounding to end the week at A$17.46, down more than seven per cent from the last close.Credit Corp, the leading debt collections firm in Australia, yielded little or nothing to its antagonists in a three-page commentary, following a trading halt on Friday.The company said it was "experiencing strong operational performance over the final quarter", for the period to June 2018, and reaffirmed guidance on its full year net profit, in a range from $62 million to $64 million. The company's rebuttal responded to a report circulating since the middle of last week that had highlighted the risks around the company's Wallet Wizard product and vulnerability to loss of bank funding and ASIC intervention. The Australian has reported that this report is the work of "an organisation called Checkmate Research … the Checkmate report did not include any disclosures or identify the authors."Credit Corp described the report as "not credible", "confused", "selective" and "erroneous", while setting out a narrative refuting all central themes of the report.