Apple Inc. reintroduced a critical vulnerability in Leopard, the newest version of Mac OS X, that it had patched more than 20 months ago in Tiger, security experts said this week.A bug in Apple Mail — the e-mail client included in Mac OS X — that Apple fixed in Tiger on March 1, 2006, has cropped up in Leopard, according to security researchers from Symantec Corp. and Intego Inc. Attackers can use the new-old vulnerability to hide malicious code in seemingly harmless file attachments and get Apple Mail to run the malware without warning the user, as it is designed to do, said Symantec in a warning to customers of its DeepSight threat management service.The Heise Security Web site first noted the returned flaw and said attackers could disguise their code as a benign file — a JPG image file, for example — then exploit the file’s “resource fork” to launch Terminal, the Mac OS X command line interface, which in turn would run a camouflaged code. The site even produced a harmless proof-of-concept e-mail attachment that demonstrated an exploit of the bug.“On a current installation of the Tiger OS, Apple Mail issues a warning that the supposed image file is a[n executable] program and is to be opened with Terminal,” Heise reported. “Apple apparently either did not incorporate this update into Leopard, or did not do it correctly.” Intego, the antivirus software vendor that earlier this month warned of an in-the-wild Mac Trojan horse, noted that Leopard’s security system does not notify users as does Tiger’s did. “The bug causing this has to do with the way Leopard manages [download] quarantines,” Intego said in an alert. “The first time a user opens an attachment, Mail opens the file directly without passing through the quarantine system.”Apple patched Tiger to ensure that its e-mail program would warn users of unsafe files as part of its Security Update 2006-001, which was released last year. Until Apple fixes Leopard, Symantec told users to use caution when handling e-mail attachments received in Mail. Intego gave similar advice: “It is important that users do not open attachments from unknown senders, especially those that come with spam messages,” its alert said.By Gregg Keizer, Computerworld (US online) Related content feature Top cybersecurity M&A deals for 2023 Fears of recession, rising interest rates, mass tech layoffs, and conservative spending trends are likely to make dealmakers cautious, but an ever-increasing need to defend against bigger and faster attacks will likely keep M&A activity steady in By CSO Staff Sep 22, 2023 24 mins Mergers and Acquisitions Mergers and Acquisitions Mergers and Acquisitions brandpost Unmasking ransomware threat clusters: Why it matters to defenders Similar patterns of behavior among ransomware treat groups can help security teams better understand and prepare for attacks By Joan Goodchild Sep 21, 2023 3 mins Cybercrime news analysis China’s offensive cyber operations support “soft power” agenda in Africa Researchers track Chinese cyber espionage intrusions targeting African industrial sectors. By Michael Hill Sep 21, 2023 5 mins Advanced Persistent Threats Cyberattacks Critical Infrastructure brandpost Proactive OT security requires visibility + prevention You cannot protect your operation by simply watching and waiting. It is essential to have a defense-in-depth approach. By Austen Byers Sep 21, 2023 4 mins Security Podcasts Videos Resources Events SUBSCRIBE TO OUR NEWSLETTER From our editors straight to your inbox Get started by entering your email address below. Please enter a valid email address Subscribe