pgsql: Obstruct EXTRACT() field name deparse injection.

Obstruct EXTRACT() field name deparse injection.

The parser accepts any string as an EXTRACT() field name, but
deparsing does not quote and escape it accordingly. To fix, quote
and escape the field name during deparsing as needed. It might be
a good idea to validate the field name during parsing and
deparsing, too, but that is left as a future exercise.

Reported-by: Ben Morris in collaboration with Claude and Anthropic Research
Author: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Reviewed-by: Etsuro Fujita <etsuro(dot)fujita(at)gmail(dot)com>
Security: CVE-2026-15741
Backpatch-through: 14

Branch
------
REL_16_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/5e5ea74e389b0736adfc5aea3dd2ca102a997d65
Author: Nathan Bossart <nathan(at)postgresql(dot)org>

Modified Files
--------------
src/backend/utils/adt/ruleutils.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)