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chmod 666 (rw-rw-rw-)

Everyone can read and write. Device files like /dev/null use it; on regular files it is almost always a mistake.

Who can do what

Commands

chmod 666 my-file
# same thing in symbolic form:
chmod u=rw,g=rw,o=rw my-file

In ls -l output, a file with this mode shows as -rw-rw-rw- and a directory as drw-rw-rw-.

Try a different mode