PHP error on logout.

I suspect this is being caused by the @ symbols in our usernames. We are authentication via LDAP using the UserPrincipalName. This has been the case for years. just seems to be a problem after updating recently.

Version: 23.11.13173 (14th November 2023)

On logout:
Unsupported key character detected: "@". Please check: https://github.com/PHPSocialNetwork/phpfastcache/wiki/%5BV6%5D-Unsupported-characters-in-key-identifiers in /opt/observium/libs/Phpfastcache8/Core/Pool/CacheItemPoolTrait.php:124

#0: (unknown function) called at [/opt/observium/libs/Phpfastcache8/Core/Pool/CacheItemPoolTrait.php:124]

119: * due to performance issue on huge
120: * loop dispatching operations
121: */
122: if (!isset($this->itemInstances[$key]) || !$this->getConfig()->isUseStaticItemCaching()) {
123: if (\preg_match('_{([' . \preg_quote(self::$unsupportedKeyChars, '~') . ']+)}', $key, $matches)) {
124: throw new PhpfastcacheInvalidArgumentException(
125: 'Unsupported key character detected: "' . $matches[1] . '". Please check: https://github.com/PHPSocialNetwork/phpfastcache/wiki/%5BV6%5D-Unsupported-characters-in-key-identifiers'
126: );
{{127: }}}
128:
129: $cacheSlamsSpendSeconds = 0;

#1: getItem called at [/opt/observium/libs/Phpfastcache8/Core/Pool/TaggableCacheItemPoolTrait.php:88]

83: * @throws PhpfastcacheInvalidArgumentException
84: */
85: protected function fetchItemsByTagFromBackend(string $tagName): array
86: {
87: if (\is_string($tagName)) {
88: $driverResponse = $this->getItem($this->getTagKey($tagName));
89: if ($driverResponse->isHit()) {
90: $tagsItems = (array)$driverResponse->get();
91:
92: /**
93: * getItems() may provides expired item(s)

#2: fetchItemsByTagFromBackend called at [/opt/observium/libs/Phpfastcache8/Core/Pool/TaggableCacheItemPoolTrait.php:52]

47: public function getItemsByTags(array $tagNames, int $strategy = TaggableCacheItemPoolInterface::TAG_STRATEGY_ONE): array
48: {
49: $items = [];
50: foreach (\array_unique($tagNames) as $tagName) {
51: if (\is_string($tagName)) {
52: $items[] = $this->fetchItemsByTagFromBackend($tagName);
53: } else {
54: throw new PhpfastcacheInvalidArgumentException('$tagName must be a a string');
{{55: }}}
{{56: }}}
57:

#3: getItemsByTags called at [/opt/observium/libs/Phpfastcache8/Core/Pool/TaggableCacheItemPoolTrait.php:131]

126: */
127: public function deleteItemsByTags(array $tagNames, int $strategy = TaggableCacheItemPoolInterface::TAG_STRATEGY_ONE): bool
128: {
129: $return = null;
130:
131: foreach ($this->getItemsByTags($tagNames, $strategy) as $item) {
132: $result = $this->deleteItem($item->getKey());
133: if ($return !== false) {
134: $return = $result;
{{135: }}}
{{136: }}}

#4: deleteItemsByTags called at [/opt/observium/includes/cache.inc.php:255]

250: } else {
251: // Cache not enabled
252: return;
{{253: }}}
254:
255: return $observium_cache->deleteItemsByTags($tags);
{{256: }}}
257:
258: /**
259: * Delete expired Items.
260: * Used "workaround" as described here:

#5: del_cache_items called at [/opt/observium/html/includes/sessions.inc.php:143]

138: // Clean cache if possible
139: $cache_tags = ['__anonymous'];
140: if ($_SESSION['authenticated']) {
141: $cache_tags = ['__username=' . $_SESSION['username']];
{{142: }}}
143: del_cache_items($cache_tags);
144:
145: // Unset session
146: @session_start();
147: if ($relogin) {
148: // Reset session and relogin (for example: HTTP auth)

#6: session_logout called at [/opt/observium/html/includes/authenticate.inc.php:142]

137: if ($_SESSION['authenticated'] && str_starts(ltrim($_SERVER['REQUEST_URI'], '/'), 'logout')) {
138: // Do not use $vars and get_vars here!
139: //print_vars($_SERVER['REQUEST_URI']);
140: if (auth_can_logout()) {
141: // No need for a feedback message if user requested a logout
142: session_logout(function_exists('auth_require_login'));
143:
144: $redirect = auth_logout_url();
145: if ($redirect) {
146: redirect_to_url($redirect);
147: exit();

#7: include called at [/opt/observium/html/index.php:72]

67: $_SERVER['PATH_INFO'] = $_SERVER['PATH_INFO'] ?? ($_SERVER['ORIG_PATH_INFO'] ?? '');
68:
69: // Clean global $vars variable, it populated only after correct authenticating
70: unset($vars);
71:
72: include($config['html_dir'] . "/includes/authenticate.inc.php");
73:
74: // Default theme set in global or user setting
75: if ($config['web_theme_default'] === 'system' && isset($_COOKIE['screen_scheme'])) {
76: $theme = $_COOKIE['screen_scheme'];
77: } else {