TF2 Item Format helps users format TF2 items to the community standards. Versions of `tf2-item-format` since at least `4.2.6` and prior to `5.9.14` are vulnerable to a Regular Expression Denial of Service (ReDoS) attack when parsing crafted user input. This vulnerability can be exploited by an attacker to perform DoS attacks on any service that uses any `tf2-item-format` to parse user input. Version `5.9.14` contains a fix for the issue.
The product uses a regular expression that either (1) contains an executable component with user-controlled inputs, or (2) allows a user to enable execution by inserting pattern modifiers.