PYSEC-2026-319 Crawl4AI: AST Sandbox Escape via gi_frame.f_back Chain - Pre-Auth RCE in Docker API

Summary The safeevalexpression function in the computed fields feature uses an AST validator that only blocks attributes starting with underscore. Python generator and frame object attributes giframe, fback, fbuiltins do NOT start with underscore, enabling a complete sandbox escape to achieve...