Weblate is a web-based continuous localization platform used to manage software translations. In versions prior to 2026.7, a user with the built-in "Edit source" role can store a malicious regular expression in a source string's flags that is executed without any timeout, allowing them to stall requests and deny service. Regular expressions supplied through the regex: quality check and regex placeholders are compiled during validation but later run against translation content in RegexCheck and PlaceholderCheck with no time limit, so a catastrophic-backtracking pattern like ^(a|aa)+$ can consume CPU indefinitely. Because Weblate re-runs these checks for every linked target unit in the same request when a source unit's flags change, a single edit can trigger sustained CPU-bound denial of service. This issue is fixed in version 2026.7.