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diff --git a/tests/t0303-robustness.sh b/tests/t0303-robustness.sh
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+#!/bin/sh
+
+# Regression tests from the September 2026 audit. Each case is a config,
+# repository or request that used to crash cgit, end it inside git, or hand
+# a visitor something other than what was asked for.
+
+test_description='Check the audit regressions'
+. ./setup.sh
+
+test_expect_success 'set up a repository and a config to vary' '
+	mkrepo repos/rob 3 &&
+	sha=$(git -C repos/rob rev-parse HEAD~1) &&
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "snapshots=tar.gz" &&
+		echo "repo.url=rob" &&
+		echo "repo.path=$PWD/repos/rob/.git"
+	} >robrc
+'
+
+robq() { CGIT_CONFIG="$PWD/robrc" QUERY_STRING="$1" cgit; }
+
+test_expect_success 'a repository without a path answers 404' '
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "repo.url=nopath" &&
+		echo "repo.url=emptypath" &&
+		echo "repo.path="
+	} >nopathrc &&
+	for r in nopath emptypath
+	do
+		CGIT_CONFIG="$PWD/nopathrc" QUERY_STRING="url=$r/log/" cgit >tmp &&
+		grep "^Status: 404 Not Found" tmp &&
+		grep "Failed to open $r: Not a valid git repository" tmp || return 1
+	done
+'
+
+test_expect_success 'a repository with an empty url is skipped with a warning' '
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "repo.url=" &&
+		echo "repo.path=$PWD/repos/rob/.git" &&
+		echo "repo.url=rob" &&
+		echo "repo.path=$PWD/repos/rob/.git"
+	} >nourlrc &&
+	CGIT_CONFIG="$PWD/nourlrc" QUERY_STRING="url=rob/" cgit >tmp 2>err &&
+	grep "^Status: 200" tmp &&
+	grep "Ignoring repository with an empty url" err
+'
+
+test_expect_success 'a scan path that is itself a repository is named after it' '
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "remove-suffix=1" &&
+		echo "scan-path=$PWD/repos/rob"
+	} >rootrc &&
+	CGIT_CONFIG="$PWD/rootrc" QUERY_STRING="url=" cgit >tmp &&
+	grep "toplevel-repo.><a href=./rob/.>rob</a>" tmp
+'
+
+test_expect_success 'a repo key after scan-path is reported instead of applied' '
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "repo.url=first" &&
+		echo "repo.path=$PWD/repos/rob/.git" &&
+		echo "scan-path=$PWD/repos" &&
+		echo "repo.desc=misplaced"
+	} >stalerc &&
+	CGIT_CONFIG="$PWD/stalerc" QUERY_STRING="url=" cgit >tmp 2>err &&
+	! grep "misplaced" tmp &&
+	grep "Ignoring repo.desc before any repo.url" err
+'
+
+test_expect_success 'a valueless or broken git config in a scanned repository is skipped' '
+	git clone -q --bare repos/rob/.git scan/a.git &&
+	printf "[cgit]\n\thide\n[cgit\n" >>scan/a.git/config &&
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "enable-git-config=1" &&
+		echo "scan-path=$PWD/scan"
+	} >gitcfgrc &&
+	CGIT_CONFIG="$PWD/gitcfgrc" QUERY_STRING="url=" cgit >tmp 2>err &&
+	grep "toplevel-repo.><a href=./a.git/.>" tmp &&
+	grep "Ignoring unreadable config in $PWD/scan/a.git/config" err
+'
+
+test_expect_success 'only descriptive keys are taken from a scanned repository' '
+	git clone -q --bare repos/rob/.git scan/b.git &&
+	{
+		echo "desc=from the repo" &&
+		echo "readme=master:file-1" &&
+		echo "head-content=<script>alert(1)</script>" &&
+		echo "logo-link=javascript:alert(2)"
+	} >scan/b.git/cgitrc &&
+	CGIT_CONFIG="$PWD/gitcfgrc" QUERY_STRING="url=b.git/about/" cgit >tmp 2>err &&
+	grep "from the repo" tmp &&
+	grep "pre class=.plaintext." tmp &&
+	! grep "alert(" tmp &&
+	grep "Ignoring head-content in $PWD/scan/b.git/: trust-scan-config is not set" err &&
+	grep "Ignoring logo-link in " err
+'
+
+test_expect_success 'a filesystem readme from a scanned repository is refused' '
+	echo "readme=/etc/hosts" >scan/b.git/cgitrc &&
+	CGIT_CONFIG="$PWD/gitcfgrc" QUERY_STRING="url=b.git/about/" cgit >tmp 2>err &&
+	grep "Ignoring readme in " err
+'
+
+test_expect_success SYMLINKS 'a symlink cycle under the scan path is entered once' '
+	ln -s . scan/loop &&
+	CGIT_CONFIG="$PWD/gitcfgrc" QUERY_STRING="url=" cgit >tmp &&
+	test $(grep -c "toplevel-repo" tmp) = 2
+'
+
+test_expect_success 'a bare query parameter does not swallow the next one' '
+	robq "url=rob/commit/&x&id=$sha" >tmp &&
+	grep "<div class=.commit-subject.>commit 2" tmp
+'
+
+test_expect_success 'a filter that cannot run answers one error page' '
+	{
+		echo "commit-filter=exec:$PWD/no/such/filter" &&
+		cat robrc
+	} >badfilterrc &&
+	CGIT_CONFIG="$PWD/badfilterrc" QUERY_STRING="url=rob/commit/" cgit >tmp 2>err &&
+	test $(grep -c "^Status:" tmp) = 1 &&
+	grep "Unable to complete the request" tmp &&
+	grep "Unable to run filter $PWD/no/such/filter" err &&
+	grep "Unable to exec filter" err
+'
+
+test_expect_success 'a filter that exits without reading does not end cgit' '
+	{
+		echo "email-filter=exec:/usr/bin/true" &&
+		cat robrc
+	} >truerc &&
+	CGIT_CONFIG="$PWD/truerc" QUERY_STRING="url=rob/log/" cgit >tmp &&
+	grep "^Status:" tmp
+'
+
+test_expect_success 'a commit encoding header is read without its newline' '
+	(
+		cd repos/rob &&
+		echo more >file-1 &&
+		git add file-1 &&
+		git -c i18n.commitEncoding=ISO-8859-1 commit -m "$(printf "caf\351")"
+	) &&
+	robq "url=rob/commit/" >tmp &&
+	grep "<div class=.commit-subject.>caf$(printf "\303\251")<" tmp
+'
+
+test_expect_success 'a submodule below the about path does not end the request' '
+	(
+		cd repos/rob &&
+		git update-index --add --cacheinfo 160000,$sha,sub &&
+		git commit -m gitlink
+	) &&
+	{
+		echo "mimetype.png=image/png" &&
+		cat robrc &&
+		echo "repo.readme=master:file-1"
+	} >aboutrc &&
+	CGIT_CONFIG="$PWD/aboutrc" QUERY_STRING="url=rob/about/sub" cgit >tmp 2>err &&
+	grep "^Status:" tmp &&
+	! grep "fatal" err
+'
+
+test_expect_success 'a missing image on the about page errors as html' '
+	CGIT_CONFIG="$PWD/aboutrc" QUERY_STRING="url=rob/about/missing.png" cgit >tmp &&
+	grep "^Status: 404" tmp &&
+	grep "^Content-Type: text/html" tmp
+'
+
+test_expect_success 'a snapshot name holding a slash is refused' '
+	robq "url=rob/snapshot/:/../../...tar.gz" >tmp &&
+	grep "^Status: 404" tmp &&
+	robq "url=rob/snapshot/rob-master.tar.gz" >tmp &&
+	grep "^Status: 200" tmp
+'
+
+test_expect_success 'a path opening with a colon is refused on the log and patch pages' '
+	robq "url=rob/log/:%25x" >tmp &&
+	grep "^Status: 400" tmp &&
+	robq "url=rob/patch/:%25x" >tmp &&
+	grep "^Status: 400" tmp &&
+	test $(grep -c "^Status:" tmp) = 1
+'
+
+test_expect_success 'a revision spelled like an option is refused' '
+	git -C repos/rob update-ref refs/heads/--stdin HEAD &&
+	robq "url=rob/log/&h=--stdin" >tmp &&
+	grep "^Status: 404" tmp &&
+	robq "url=rob/blame/file-1&id=--stdin" >tmp &&
+	grep "^Status: 400" tmp &&
+	robq "url=rob/atom/&h=--stdin" >tmp &&
+	grep "^Status: 404" tmp
+'
+
+test_expect_success 'the blob page reads a file through an annotated tag' '
+	git -C repos/rob -c tag.gpgsign=false tag -a -m note ann HEAD &&
+	robq "url=rob/blob/&h=ann&path=file-1" >tmp &&
+	strip_headers <tmp >body &&
+	printf "more\n" >want &&
+	test_cmp want body
+'
+
+test_expect_success 'the commit page shows a message whole when text follows its trailers' '
+	(
+		cd repos/rob &&
+		echo again >file-1 &&
+		git add file-1 &&
+		git commit -F - <<-\EOF
+		Subject
+
+		Body text.
+
+		Signed-off-by: A U Thor <author@example.com>
+
+		Conflicts:
+			file-1
+		EOF
+	) &&
+	{
+		echo "enable-trailers=1" &&
+		cat robrc
+	} >trailrc &&
+	CGIT_CONFIG="$PWD/trailrc" QUERY_STRING="url=rob/commit/" cgit >tmp &&
+	! grep "commit-trailers" tmp &&
+	grep "Conflicts:" tmp
+'
+
+test_expect_success 'a revision expression that walks the history is refused' '
+	robq "url=rob/log/&h=:/zzzz" >tmp &&
+	grep "^Status: 404" tmp &&
+	robq "url=rob/commit/&id=HEAD^{/zzzz}" >tmp &&
+	grep "^Status: 400" tmp &&
+	robq "url=rob/log/&qt=range&q=:/zzzz" >tmp &&
+	grep "^Status: 400" tmp &&
+	robq "url=rob/log/&qt=range&q=master~1..master" >tmp &&
+	grep "^Status: 400" tmp &&
+	robq "url=rob/log/&qt=range&q=$sha..master" >tmp &&
+	grep "^Status: 200" tmp
+'
+
+test_expect_success 'the log search is literal' '
+	robq "url=rob/log/&qt=grep&q=commit.1" >tmp &&
+	! grep ">commit 1</a>" tmp &&
+	robq "url=rob/log/&qt=grep&q=commit%201" >tmp &&
+	grep ">commit 1</a>" tmp
+'
+
+test_expect_success 'a commit with a broken tree line does not crash the blob page' '
+	git clone -q repos/rob broken &&
+	(
+		cd broken &&
+		bad=$(git cat-file commit HEAD | sed "s/^tree .*/tree not-a-hash/" |
+			git hash-object -t commit -w --stdin --literally) &&
+		echo $bad >.git/refs/heads/bad
+	) &&
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "repo.url=broken" &&
+		echo "repo.path=$PWD/broken/.git" &&
+		echo "repo.readme=:file-1"
+	} >brokenrc &&
+	CGIT_CONFIG="$PWD/brokenrc" QUERY_STRING="url=broken/blob/&h=bad&path=file-1" cgit >tmp &&
+	grep "^Status: 404" tmp
+'
+
+test_expect_success 'a die inside git answers one 500 page and logs the reason' '
+	printf "[core\n" >>broken/.git/config &&
+	CGIT_CONFIG="$PWD/brokenrc" QUERY_STRING="url=broken/log/" cgit >tmp 2>err &&
+	grep "^Status: 500" tmp &&
+	test $(grep -c "^Status:" tmp) = 1 &&
+	grep "bad config line" err &&
+	! grep "bad config line" tmp
+'
+
+test_expect_success 'a history with a missing parent renders up to the gap' '
+	git clone -q repos/rob gap &&
+	older=$(git -C gap rev-parse HEAD~3) &&
+	parent=$(git -C gap rev-parse HEAD~2) &&
+	rm gap/.git/objects/$(echo $parent | cut -c1-2)/$(echo $parent | cut -c3-) &&
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "repo.url=gap" &&
+		echo "repo.path=$PWD/gap/.git"
+	} >gaprc &&
+	CGIT_CONFIG="$PWD/gaprc" QUERY_STRING="url=gap/log/" cgit >tmp 2>err &&
+	test $(grep -c "^Status:" tmp) = 1 &&
+	grep "Unable to complete the request" tmp &&
+	grep "Failed to traverse parents" err &&
+	CGIT_CONFIG="$PWD/gaprc" QUERY_STRING="url=gap/patch/&id2=$older" cgit >tmp &&
+	test $(grep -c "^Status:" tmp) = 1 &&
+	grep "^Status: 500" tmp
+'
+
+test_expect_success 'a filter pipeline sees the default SIGPIPE disposition' '
+	cat >pipe.sh <<-\EOF &&
+	#!/bin/sh
+	n=0
+	while test $n -lt 20000
+	do
+		echo line
+		n=$((n + 1))
+	done | head -c 5
+	EOF
+	chmod +x pipe.sh &&
+	{
+		echo "source-filter=exec:$PWD/pipe.sh" &&
+		cat robrc
+	} >piperc &&
+	CGIT_CONFIG="$PWD/piperc" QUERY_STRING="url=rob/tree/file-1" cgit >tmp 2>err &&
+	grep "^Status: 200" tmp &&
+	! grep -i "broken pipe" err
+'
+
+test_expect_success 'the fallback branch skips a name spelled like an option' '
+	git -C repos/rob update-ref refs/heads/-first HEAD &&
+	git -C repos/rob symbolic-ref HEAD refs/heads/gone &&
+	robq "url=rob/" >tmp &&
+	git -C repos/rob symbolic-ref HEAD refs/heads/master &&
+	grep "^Status: 200" tmp
+'
+
+test_expect_success 'a blank line in the mimetype file is skipped' '
+	(
+		cd repos/rob &&
+		echo note >note.cgt &&
+		git add note.cgt &&
+		git commit -m note
+	) &&
+	printf "\n   \nimage/x-cgit cgt\n" >mime.types &&
+	{
+		echo "mimetype-file=$PWD/mime.types" &&
+		cat robrc
+	} >mimerc &&
+	CGIT_CONFIG="$PWD/mimerc" QUERY_STRING="url=rob/plain/note.cgt" cgit >tmp &&
+	grep "^Content-Type: image/x-cgit" tmp
+'
+
+test_expect_success 'a refs page named with an id is not cached for ever' '
+	mkdir -p cache &&
+	{
+		echo "cache-size=10" &&
+		echo "cache-root=$PWD/cache" &&
+		echo "cache-static-ttl=-1" &&
+		echo "cache-dynamic-ttl=0" &&
+		echo "cache-summary-ttl=0" &&
+		grep -v "^cache-size" robrc
+	} >ttlrc &&
+	full=$(git -C repos/rob rev-parse HEAD) &&
+	CGIT_CONFIG="$PWD/ttlrc" QUERY_STRING="url=rob/refs/&id=$full" cgit >tmp &&
+	git -C repos/rob tag later HEAD &&
+	CGIT_CONFIG="$PWD/ttlrc" QUERY_STRING="url=rob/refs/&id=$full" cgit >tmp &&
+	grep ">later<" tmp
+'
+
+test_expect_success 'the diff caps hold when the path names a directory' '
+	(
+		cd repos/rob &&
+		mkdir -p dir &&
+		for n in 1 2 3
+		do
+			echo $n >dir/f$n || return 1
+		done &&
+		git add dir &&
+		git commit -m dir
+	) &&
+	{
+		echo "max-diff-files=2" &&
+		cat robrc
+	} >caprc &&
+	CGIT_CONFIG="$PWD/caprc" QUERY_STRING="url=rob/diff/dir" cgit >tmp &&
+	grep "too large to be rendered inline" tmp &&
+	CGIT_CONFIG="$PWD/caprc" QUERY_STRING="url=rob/diff/dir/f1" cgit >tmp &&
+	! grep "too large to be rendered inline" tmp
+'
+
+test_expect_success 'a snapshot of a tag spelled like an option is archived' '
+	git -C repos/rob update-ref refs/tags/-l HEAD &&
+	robq "url=rob/snapshot/-l.tar.gz" >tmp &&
+	grep "^Status: 200" tmp &&
+	strip_headers <tmp | gzip -dc | tar -tf - >list &&
+	grep "file-1" list
+'
+
+test -n "$CGIT_VALGRIND" || test_set_prereq NO_VALGRIND
+
+test_expect_success NO_VALGRIND 'a snapshot format whose compressor is missing answers 500' '
+	{
+		echo "snapshots=tar.xz" &&
+		grep -v "^snapshots" robrc
+	} >xzrc &&
+	cgitbin=$(command -v cgit) &&
+	mkdir -p nobin &&
+	PATH="$PWD/nobin" CGIT_CONFIG="$PWD/xzrc" \
+		QUERY_STRING="url=rob/snapshot/rob-master.tar.xz" $cgitbin >tmp &&
+	grep "^Status: 500" tmp &&
+	test $(grep -c "^Status:" tmp) = 1
+'
+
+test_expect_success 'a disk readme in the repository directory serves no sibling' '
+	echo hello >repos/rob/.git/README &&
+	{
+		cat robrc &&
+		echo "repo.readme=README"
+	} >diskrc &&
+	CGIT_CONFIG="$PWD/diskrc" QUERY_STRING="url=rob/about/" cgit >tmp &&
+	grep "hello" tmp &&
+	CGIT_CONFIG="$PWD/diskrc" QUERY_STRING="url=rob/about/config" cgit >tmp &&
+	! grep "repositoryformatversion" tmp
+'
+
+test_expect_success 'a tag pointing at a tag links the inner tag by id' '
+	git -C repos/rob -c tag.gpgsign=false tag -a -m outer outer ann &&
+	inner=$(git -C repos/rob rev-parse ann) &&
+	robq "url=rob/tag/&id=$inner" >tmp &&
+	grep "^Status: 200" tmp &&
+	grep "tagged object" tmp
+'
+
+test_expect_success 'the dumb transport serves an empty repository' '
+	git init -q --bare empty.git &&
+	{
+		echo "virtual-root=/" &&
+		echo "cache-size=0" &&
+		echo "repo.url=empty" &&
+		echo "repo.path=$PWD/empty.git"
+	} >emptyrc &&
+	CGIT_CONFIG="$PWD/emptyrc" QUERY_STRING="url=empty/info/refs" cgit >tmp &&
+	grep "^Status: 200" tmp &&
+	grep "^Content-Type: text/plain" tmp &&
+	CGIT_CONFIG="$PWD/emptyrc" QUERY_STRING="url=empty/objects/info" cgit >tmp &&
+	grep "^Status: 404" tmp
+'
+
+test_expect_success 'a symlink whose target is a large blob is listed without it' '
+	big=$(head -c 5000 /dev/zero | tr "\0" a | git -C repos/rob hash-object -w --stdin) &&
+	(
+		cd repos/rob &&
+		git update-index --add --cacheinfo 120000,$big,biglink &&
+		git commit -m biglink
+	) &&
+	robq "url=rob/tree/" >tmp &&
+	grep "biglink" tmp &&
+	! grep "aaaaaaaaaa" tmp
+'
+
+test_expect_success 'a chain of single directories is followed a bounded number of levels' '
+	(
+		cd repos/rob &&
+		deep=$(printf "d/%.0s" $(seq 1 40))leaf &&
+		mkdir -p $(dirname $deep) &&
+		echo x >$deep &&
+		git add d &&
+		git commit -m deep
+	) &&
+	robq "url=rob/tree/" >tmp &&
+	test $(grep -o "class=.ls-dir." tmp | wc -l) -le 17
+'
+
+test_done