Highlights

This release is a milestone: it fixes Black's first CVE security vulnerability. If you run Black on untrusted input, or if you habitually put thousands of leading tab characters in your docstrings, you are strongly encouraged to upgrade immediately to fix CVE-2024-21503.

This release also fixes a bug in Black's AST safety check that allowed Black to make incorrect changes to certain f-strings that are valid in Python 3.12 and higher.

Stable style

• Don't move comments along with delimiters, which could cause crashes (#4248)
• Strengthen AST safety check to catch more unsafe changes to strings. Previous versions of Black would incorrectly format the contents of certain unusual f-strings containing nested strings with the same quote type. Now, Black will crash on such strings until support for the new f-string syntax is implemented. (#4270)
• Fix a bug where line-ranges exceeding the last code line would not work as expected (#4273)

Performance

• Fix catastrophic performance on docstrings that contain large numbers of leading tab characters. This fixes CVE-2024-21503. (#4278)

Documentation

• Note what happens when --check is used with --quiet (#4236)