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gh-74453: Add stronger security warning to os.path.commonprefix #144401

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encukou merged 3 commits into from
Feb 3, 2026
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gh-74453: Add stronger security warning to os.path.commonprefix #144401

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5704727
Add stronger security warning to os.path.commonprefix
sethmlarson Feb 2, 2026
fa43ff8
Remove duplicated recommendation to use `commonpath()`.
sethmlarson Feb 2, 2026
79e135c
Use "warning", not "danger"
sethmlarson Feb 2, 2026
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9 changes: 6 additions & 3 deletions Doc/library/os.path.rst
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Expand Up @@ -97,12 +97,15 @@ the :mod:`glob` module.)

.. function:: commonprefix(list, /)

Return the longest path prefix (taken character-by-character) that is a
prefix of all paths in *list*. If *list* is empty, return the empty string
Return the longest string prefix (taken character-by-character) that is a
prefix of all strings in *list*. If *list* is empty, return the empty string
(``''``).

.. note::
.. danger::
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@picnixz picnixz Feb 2, 2026

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We do not often use "danger" but rather prefer using warning (I believe we have something about it in the devguide)

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@sethmlarson sethmlarson Feb 2, 2026

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Thanks! I've updated to warning instead of danger.

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@StanFromIreland StanFromIreland Feb 2, 2026

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I believe we have something about it in the devguide

Out of curiosity, which section? I was unable to find any on these.

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@sethmlarson sethmlarson Feb 2, 2026

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Maybe here? https://devguide.python.org/documentation/markup/#paragraph-level-markup

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@picnixz picnixz Feb 2, 2026 •
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Yes here. It is just so that we do not have a proliferation of different boxes (while Sphinx and docutils provide lots of boxes we tend to only use a few of them). In addition other security warnings were usually indicated through a warning.

Though if we actually use danger/important instead of warning, feel free to revert my suggestion (from what I remember we mostly used warning)


If you need a **common path prefix**, then the algorithm
implemented in this function is not secure. Use
:func:`commonpath` for finding a common path prefix.
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This function may return invalid paths because it works a
character at a time. To obtain a valid path, see
:func:`commonpath`.
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