diff --git a/src/Building/PlaceholderReplacer.php b/src/Building/PlaceholderReplacer.php
index 3383aa61..95fa171f 100644
--- a/src/Building/PlaceholderReplacer.php
+++ b/src/Building/PlaceholderReplacer.php
@@ -57,6 +57,13 @@ public function replacePlaceholdersWithPlaceholderReplacements(IOInterface $io,
         foreach (new RecursiveIteratorIterator(new RecursiveDirectoryIterator($downloadedPackage->extractedSourcePath)) as $file) {
             assert($file instanceof SplFileInfo);
 
+            // Refuse to follow symlinks into files the package author did not
+            // legitimately own at build time (e.g., an archive entry that points
+            // at the invoking user's $HOME).
+            if ($file->isLink()) {
+                continue;
+            }
+
             if (! $file->isFile() || ! in_array($file->getExtension(), self::FILE_EXTENSIONS)) {
                 continue;
             }
diff --git a/src/ComposerIntegration/Listeners/OverrideDownloadUrlInstallListener.php b/src/ComposerIntegration/Listeners/OverrideDownloadUrlInstallListener.php
index 105c0052..e0f41347 100644
--- a/src/ComposerIntegration/Listeners/OverrideDownloadUrlInstallListener.php
+++ b/src/ComposerIntegration/Listeners/OverrideDownloadUrlInstallListener.php
@@ -129,6 +129,15 @@ function (OperationInterface $operation): void {
                     $this->composerRequest->pieOutput->write('Found prebuilt archive: ' . $url);
                     $composerPackage->setDistUrl($url);
 
+                    // Composer's dist-sha was computed against the original
+                    // Packagist URL; once we swap to a release-asset URL the
+                    // FileDownloader has nothing to validate the new bytes
+                    // against. Surface that so the caller knows HTTPS-to-origin
+                    // is the only integrity guarantee left.
+                    $this->composerRequest->pieOutput->write(
+                        '<warning>Note: dist-sha integrity check is not available for prebuilt-binary URLs; HTTPS to the release-asset origin is the only integrity guarantee.</warning>',
+                    );
+
                     if (pathinfo($url, PATHINFO_EXTENSION) === 'tgz') {
                         $composerPackage->setDistType('tar');
                     }
diff --git a/src/ConfigureOption.php b/src/ConfigureOption.php
index 12657a59..f4dca0ad 100644
--- a/src/ConfigureOption.php
+++ b/src/ConfigureOption.php
@@ -28,6 +28,14 @@ public static function fromComposerJsonDefinition(array $configureOptionDefiniti
     {
         Assert::keyExists($configureOptionDefinition, 'name');
         Assert::stringNotEmpty($configureOptionDefinition['name']);
+        // Restrict to identifier characters that match real ./configure flag
+        // conventions. Whitespace and shell metacharacters in this field flow
+        // verbatim into argv, log output, and installed.json metadata.
+        Assert::regex(
+            $configureOptionDefinition['name'],
+            '/^[a-zA-Z][a-zA-Z0-9_-]*$/',
+            'php-ext.configure-options[].name must be a configure-flag identifier (got %s)',
+        );
 
         $needsValue = false;
         if (array_key_exists('needs-value', $configureOptionDefinition)) {
diff --git a/src/Installing/Ini/RemoveIniEntryWithFileGetContents.php b/src/Installing/Ini/RemoveIniEntryWithFileGetContents.php
index 96abe3e6..15414ee0 100644
--- a/src/Installing/Ini/RemoveIniEntryWithFileGetContents.php
+++ b/src/Installing/Ini/RemoveIniEntryWithFileGetContents.php
@@ -19,6 +19,7 @@
 use function file_exists;
 use function in_array;
 use function is_dir;
+use function preg_quote;
 use function Safe\file_get_contents;
 use function Safe\preg_replace;
 use function Safe\scandir;
@@ -67,10 +68,14 @@ static function (string $path) use ($additionalIniDirectory): bool {
         // Make sure all symlinks are resolved
         $allIniFiles = array_filter(array_map('realpath', $allIniFiles));
 
+        // Anchor on the right with \b so uninstalling `foo` doesn't also
+        // rewrite the prefix of `extension=foo_other`. preg_quote on the
+        // extension name is defence-in-depth in case future ExtensionName
+        // validation ever loosens past `^[A-Za-z][a-zA-Z0-9_]+$`.
         $regex = sprintf(
-            '/^(%s\s*=\s*%s)/m',
+            '/^(%s\s*=\s*%s)\b/m',
             $package->extensionType() === ExtensionType::PhpModule ? 'extension' : 'zend_extension',
-            $package->extensionName()->name(),
+            preg_quote($package->extensionName()->name(), '/'),
         );
 
         $updatedIniFiles = [];
diff --git a/src/Installing/WindowsInstall.php b/src/Installing/WindowsInstall.php
index 21a7f5e4..ae5e38ec 100644
--- a/src/Installing/WindowsInstall.php
+++ b/src/Installing/WindowsInstall.php
@@ -58,10 +58,13 @@ public function __invoke(
             assert($file instanceof SplFileInfo);
 
             /**
-             * Skip directories, the main DLL, PDB
+             * Skip directories, the main DLL, PDB, and any symlinks the archive
+             * may have shipped (symlink-followed targets fall outside the source
+             * dir's containment guarantees).
              */
             if (
                 $file->isDir()
+                || $file->isLink()
                 || $this->normalisedPathsMatch($file->getPathname(), $sourceDllName)
                 || $this->normalisedPathsMatch($file->getPathname(), $sourcePdbName)
             ) {
diff --git a/src/SelfManage/Verify/FallbackVerificationUsingOpenSsl.php b/src/SelfManage/Verify/FallbackVerificationUsingOpenSsl.php
index 3c2a80ae..e62e3cdf 100644
--- a/src/SelfManage/Verify/FallbackVerificationUsingOpenSsl.php
+++ b/src/SelfManage/Verify/FallbackVerificationUsingOpenSsl.php
@@ -36,9 +36,12 @@ public function __construct(
 
     public function verify(ReleaseMetadata $releaseMetadata, BinaryFile $pharFilename, IOInterface $io): void
     {
-        $io->write(
-            'Falling back to basic verification. To use full verification, install the `gh` CLI tool.',
-            verbosity: IOInterface::VERBOSE,
+        // The fallback verifier checks cert chain, cert extension claims, DSSE
+        // subject digest, and DSSE signature, but does NOT validate Rekor
+        // transparency-log inclusion. `gh attestation verify` does. Surface the
+        // reduced guarantees so users on shared / air-gapped hosts know.
+        $io->writeError(
+            '<warning>Falling back to OpenSSL verification (no Rekor inclusion check). Install `gh` for full attestation verification.</warning>',
         );
 
         try {