Twig: Sandbox `__toString()` policy bypass via dynamic mapping keys

Description This is a residual bypass of CVE-2026-47732 / GHSA-pr2w-4gpj-cpq4 left after the initial fix for unguarded toString calls. In 3.26.0 the sandbox visitor was extended to wrap every child node that its parent will string-coerce at runtime with CheckToStringNode, gated by the new...

GHSA-PR2W-4GPJ-CPQ4 Twig: Sandbox: multiple `__toString()` policy bypasses via unguarded string coercion points

Description SandboxNodeVisitor enforces SecurityPolicy::checkMethodAllowed for implicit toString calls by wrapping selected AST nodes in CheckToStringNode. The set of wrapped nodes is incomplete, and several Twig language constructs still trigger PHP string coercion on a Stringable operand withou...