A second Citadel Investment Group high-frequency trading programmer has pleaded guilty to charges that he sought to cover up a scheme to steal the firm’s software. Sahil Uppal pleaded guilty to obstructing an investigation into his colleague, Yihao Pu. Pu pleaded guilty to taking proprietary information from Citadel last week. Uppal, who worked with Pu at an unidentified New Jersey firm before both moved to Citadel within months of one another in 2010, said he had transferred three quantitative trading scripts he wrote for Citadel to Pu without permission. When Citadel confronted Pu in 2011 about his activities, Uppal and another person went to Pu’s apartment to remove computer equipment. Uppal and Pu will be sentenced on Nov. 7.