Enhanced Sed Command Validation

What: Significantly improved security validation for sed commands to prevent dangerous operations while allowing safe read-only usage.

How it works: The validation now uses a comprehensive whitelist approach with multiple layers:

1. Pre-parsing flag detection - Blocks dangerous flag combinations like -ew, -we before parsing
2. Whitelist validation - Only allows two safe patterns:

• Print-only operations with -n flag (e.g., sed -n '1,10p' file.txt)
• Simple substitutions with safe flags (e.g., sed 's/old/new/' file.txt)

1. Comprehensive blacklist - Blocks 15+ dangerous patterns including:

• Write commands (w, W)
• Execute commands (e, E)
• Non-ASCII characters and escape sequences
• Command chaining with semicolons in certain contexts
• Braces, negation operators, and other advanced features

Details:

• Builds upon existing sed validation from v2.0.30 (function hoB at line 209135)
• Adds four new validation helpers: Aj8() at line 209202, Bj8() at line 209245, Qj8() at line 209254, Zj8() at line 209384
• New validation function JtB() at line 209288 replaces hoB
• Dangerous flag combination detection in Gj8() at line 209345
• Prevents file modification and command execution while allowing safe text processing
• Evidence: Comparison of hoB() at line 209135 in v2.0.30 vs JtB() at line 209288 in v2.0.31