GHSA-c875-h985-hvrc: Scriban: Built-in operations bypass LoopLimit and delay cancellation, enabling Denial of Service

Summary Scriban's LoopLimit only applies to script loop statements, not to expensive iteration performed inside operators and builtins. An attacker can submit a single expression such as {{ 1..1000000 | array.size }} and force large amounts of CPU work even when LoopLimit is set to a very small value. Details The relevant code path is: - ScriptBlockStatement.Evaluate() calls context.CheckAbort() once per statement in src/Scriban/Syntax/Statements/ScriptBlockStatement.cs lines 41–46. - LoopLimit enforcement is tied to script loop execution via TemplateContext.StepLoop(), not to internal helper iteration. - array.size in src/Scriban/Functions/ArrayFunctions.cs lines 596–609 calls list.Cast<object>().Count() for non-collection enumerables. - 1..N creates a ScriptRange from ScriptBinaryExpression.RangeInclude() in src/Scriban/Syntax/Expressions/ScriptBinaryExpression.cs lines 745–748. - ScriptRange then yields every element one by one without going through StepLoop() in src/Scriban/Runtime/ScriptRange.cs. This means a single statement can perform arbitrarily large iteration without being stopped by LoopLimit. There is also a related memory-amplification path in string * int: - ScriptBinaryExpression.CalculateToString() appends in a plain for loop in src/Scriban/Syntax/Expressions/ScriptBinaryExpression.cs lines 301–334. Proof of Concept Setup mkdir scriban-poc3 cd scriban-poc3 dotnet new console --framework net8.0 dotnet add package Scriban --version 6.6.0 Program.cs using Scriban; var template = Template.Parse("{{ 1..1000000 | array.size }}"); var context = new TemplateContext { LoopLimit = 1 }; Console.WriteLine(template.Render(context)); Run dotnet run Actual Output 1000000 Expected Behavior A safety limit of LoopLimit = 1 should prevent a template from performing one million iterations worth of work. Opti