Add backslash coverage to wp_options LIKE escaping tests

tests/php/includes/functions/test-acf-option-meta-like-escaping.php

@@ -118,6 +118,32 @@ public function test_underscore_prefix_is_escaped() {
 		);
 	}
 
+	/**
+	 * A prefix containing a backslash must be escaped.
+	 */
+	public function test_backslash_prefix_is_escaped() {
+		global $wpdb;
+
+		// The prefix is the three characters a \ b.
+		acf_get_option_meta( 'a\\b' );
+
+		$good = $this->expected_like_fragment( 'a\\b_' );
+		$this->assertStringContainsString(
+			$good,
+			$this->captured_sql,
+			'A backslash in the prefix should be escaped via esc_like().'
+		);
+
+		// The previous str_replace() approach escaped only `_`, leaving the
+		// backslash unescaped. That exact fragment must not appear.
+		$bad = $wpdb->prepare( '%s', str_replace( '_', '\_', 'a\\b_%' ) );
+		$this->assertStringNotContainsString(
+			$bad,
+			$this->captured_sql,
+			'The pattern with an unescaped backslash must not be generated.'
+		);
+	}
+
 	/**
 	 * A benign prefix still produces the expected (unchanged) pattern.
 	 */

tests/php/includes/test-like-escaping-parity.php

@@ -102,6 +102,31 @@ public function test_upgrade_550_taxonomy_escapes_like() {
 		);
 	}
 
+	/**
+	 * Ensures acf_upgrade_550_taxonomy() also escapes a backslash.
+	 */
+	public function test_upgrade_550_taxonomy_escapes_backslash() {
+		global $wpdb;
+
+		// The taxonomy is the three characters a \ b.
+		acf_upgrade_550_taxonomy( 'a\\b' );
+
+		$query = $this->last_query();
+		$this->assertNotEmpty( $query, 'The upgrade SELECT should have been captured.' );
+		$this->assertStringContainsString(
+			$this->expected_fragment( 'a\\b_' ),
+			$query,
+			'A backslash should be escaped via esc_like().'
+		);
+
+		$bad = $wpdb->prepare( '%s', str_replace( '_', '\_', 'a\\b_%' ) );
+		$this->assertStringNotContainsString(
+			$bad,
+			$query,
+			'The pattern with an unescaped backslash must not be generated.'
+		);
+	}
+
 	/**
 	 * Ensures acf_form_taxonomy::delete_term() escapes the taxonomy and term
 	 * in its legacy (no-termmeta) DELETE.