Curl’s lead developer, Daniel Stenberg, has warned GitHub about a potential security vulnerability linked to ‘malicious Unicode.’ He revealed that a contributor recently replaced an ASCII letter with a Unicode alternative in a pull request, which went unnoticed by the team or their CI systems. The change was visually identical to its ASCII counterpart, making it impossible to detect through simple visual inspection. Stenberg emphasized that altering even a single letter in a URL could have severe consequences, depending on the context. This led Curl to implement new checks to detect such Unicode-based malicious activity. These include a new CI job designed to scan the curl git repository for UTF, ensuring that most files and content remain in plain ASCII. The team has also replaced certain UTF-8 occurrences in test files with escape sequences or ASCII equivalents to prevent similar issues in the future. Stenberg expressed hope that these changes will deter potential exploitation, though he acknowledged that security remains an ongoing challenge where proactive measures are essential. In the blog post, he initially jokingly remarked about GitHub’s lack of response, but later confirmed that the platform has taken the issue seriously and is working on a fix.