diff --git a/src/js/contentscript.js b/src/js/contentscript.js
index 05f5446a8..f7aa657cb 100644
--- a/src/js/contentscript.js
+++ b/src/js/contentscript.js
@@ -469,14 +469,10 @@ vAPI.DOMFilterer = (function() {
             }
             this.needle = new RegExp(arg0, arg1);
         }
-        exec(input) {
-            const output = [];
-            for ( const node of input ) {
-                if ( this.needle.test(node.textContent) ) {
-                    output.push(node);
-                }
+        transpose(node, output) {
+            if ( this.needle.test(node.textContent) ) {
+                output.push(node);
             }
-            return output;
         }
     };
 
@@ -484,24 +480,17 @@ vAPI.DOMFilterer = (function() {
         constructor(task) {
             this.pselector = new PSelector(task[1]);
         }
-        exec(input) {
-            const output = [];
-            for ( const node of input ) {
-                if ( this.pselector.test(node) === this.target ) {
-                    output.push(node);
-                }
+        transpose(node, output) {
+            if ( this.pselector.test(node) === this.target ) {
+                output.push(node);
             }
-            return output;
         }
     };
     PSelectorIfTask.prototype.target = true;
 
     const PSelectorIfNotTask = class extends PSelectorIfTask {
-        constructor(task) {
-            super(task);
-            this.target = false;
-        }
     };
+    PSelectorIfNotTask.prototype.target = false;
 
     const PSelectorMatchesCSSTask = class {
         constructor(task) {
@@ -512,46 +501,31 @@ vAPI.DOMFilterer = (function() {
             }
             this.value = new RegExp(arg0, arg1);
         }
-        exec(input) {
-            const output = [];
-            for ( const node of input ) {
-                const style = window.getComputedStyle(node, this.pseudo);
-                if ( style === null ) { return null; } /* FF */
-                if ( this.value.test(style[this.name]) ) {
-                    output.push(node);
-                }
+        transpose(node, output) {
+            const style = window.getComputedStyle(node, this.pseudo);
+            if ( style !== null && this.value.test(style[this.name]) ) {
+                output.push(node);
             }
-            return output;
         }
     };
     PSelectorMatchesCSSTask.prototype.pseudo = null;
 
     const PSelectorMatchesCSSAfterTask = class extends PSelectorMatchesCSSTask {
-        constructor(task) {
-            super(task);
-            this.pseudo = ':after';
-        }
     };
+    PSelectorMatchesCSSAfterTask.prototype.pseudo = ':after';
 
     const PSelectorMatchesCSSBeforeTask = class extends PSelectorMatchesCSSTask {
-        constructor(task) {
-            super(task);
-            this.pseudo = ':before';
-        }
     };
+    PSelectorMatchesCSSBeforeTask.prototype.pseudo = ':before';
 
     const PSelectorMinTextLengthTask = class {
         constructor(task) {
             this.min = task[1];
         }
-        exec(input) {
-            const output = [];
-            for ( const node of input ) {
-                if ( node.textContent.length >= this.min ) {
-                    output.push(node);
-                }
+        transpose(node, output) {
+            if ( node.textContent.length >= this.min ) {
+                output.push(node);
             }
-            return output;
         }
     };
 
@@ -559,20 +533,15 @@ vAPI.DOMFilterer = (function() {
         constructor(task) {
             this.nth = task[1];
         }
-        exec(input) {
-            const output = [];
-            for ( let node of input ) {
-                let nth = this.nth;
-                for (;;) {
-                    node = node.parentElement;
-                    if ( node === null ) { break; }
-                    nth -= 1;
-                    if ( nth !== 0 ) { continue; }
-                    output.push(node);
-                    break;
-                }
+        transpose(node, output) {
+            let nth = this.nth;
+            for (;;) {
+                node = node.parentElement;
+                if ( node === null ) { return; }
+                nth -= 1;
+                if ( nth === 0 ) { break; }
             }
-            return output;
+            output.push(node);
         }
     };
 
@@ -580,25 +549,21 @@ vAPI.DOMFilterer = (function() {
         constructor(task) {
             this.spath = task[1];
         }
-        exec(input) {
-            const output = [];
-            for ( let node of input ) {
-                const parent = node.parentElement;
-                if ( parent === null ) { continue; }
-                let pos = 1;
-                for (;;) {
-                    node = node.previousElementSibling;
-                    if ( node === null ) { break; }
-                    pos += 1;
-                }
-                const nodes = parent.querySelectorAll(
-                    ':scope > :nth-child(' + pos + ')' + this.spath
-                );
-                for ( const node of nodes ) {
-                    output.push(node);
-                }
+        transpose(node, output) {
+            const parent = node.parentElement;
+            if ( parent === null ) { return; }
+            let pos = 1;
+            for (;;) {
+                node = node.previousElementSibling;
+                if ( node === null ) { break; }
+                pos += 1;
+            }
+            const nodes = parent.querySelectorAll(
+                `:scope > :nth-child(${pos})${this.spath}`
+            );
+            for ( const node of nodes ) {
+                output.push(node);
             }
-            return output;
         }
     };
 
@@ -623,17 +588,14 @@ vAPI.DOMFilterer = (function() {
                 filterer.onDOMChanged([ null ]);
             }
         }
-        exec(input) {
-            if ( input.length === 0 ) { return input; }
+        transpose(node, output) {
+            output.push(node);
+            if ( this.observed.has(node) ) { return; }
             if ( this.observer === null ) {
                 this.observer = new MutationObserver(this.handler);
             }
-            for ( const node of input ) {
-                if ( this.observed.has(node) ) { continue; }
-                this.observer.observe(node, this.observerOptions);
-                this.observed.add(node);
-            }
-            return input;
+            this.observer.observe(node, this.observerOptions);
+            this.observed.add(node);
         }
     };
 
@@ -642,23 +604,19 @@ vAPI.DOMFilterer = (function() {
             this.xpe = document.createExpression(task[1], null);
             this.xpr = null;
         }
-        exec(input) {
-            const output = [];
-            for ( const node of input ) {
-                this.xpr = this.xpe.evaluate(
-                    node,
-                    XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,
-                    this.xpr
-                );
-                let j = this.xpr.snapshotLength;
-                while ( j-- ) {
-                    const node = this.xpr.snapshotItem(j);
-                    if ( node.nodeType === 1 ) {
-                        output.push(node);
-                    }
+        transpose(node, output) {
+            this.xpr = this.xpe.evaluate(
+                node,
+                XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,
+                this.xpr
+            );
+            let j = this.xpr.snapshotLength;
+            while ( j-- ) {
+                const node = this.xpr.snapshotItem(j);
+                if ( node.nodeType === 1 ) {
+                    output.push(node);
                 }
             }
-            return output;
         }
     };
 
@@ -677,7 +635,7 @@ vAPI.DOMFilterer = (function() {
                     [ ':not', PSelectorIfNotTask ],
                     [ ':nth-ancestor', PSelectorNthAncestorTask ],
                     [ ':spath', PSelectorSpathTask ],
-                    [ ':watch-attrs', PSelectorWatchAttrs ],
+                    [ ':watch-attr', PSelectorWatchAttrs ],
                     [ ':xpath', PSelectorXpathTask ],
                 ]);
             }
@@ -704,21 +662,27 @@ vAPI.DOMFilterer = (function() {
             let nodes = this.prime(input);
             for ( const task of this.tasks ) {
                 if ( nodes.length === 0 ) { break; }
-                nodes = task.exec(nodes);
+                const transposed = [];
+                for ( const node of nodes ) {
+                    task.transpose(node, transposed);
+                }
+                nodes = transposed;
             }
             return nodes;
         }
         test(input) {
             const nodes = this.prime(input);
-            const AA = [ null ];
             for ( const node of nodes ) {
-                AA[0] = node;
-                let aa = AA;
+                let output = [ node ];
                 for ( const task of this.tasks ) {
-                    aa = task.exec(aa);
-                    if ( aa.length === 0 ) { break; }
+                    const transposed = [];
+                    for ( const node of output ) {
+                        task.transpose(node, transposed);
+                    }
+                    output = transposed;
+                    if ( output.length === 0 ) { break; }
                 }
-                if ( aa.length !== 0 ) { return true; }
+                if ( output.length !== 0 ) { return true; }
             }
             return false;
         }
diff --git a/src/js/html-filtering.js b/src/js/html-filtering.js
index e79fd401c..5e2db800d 100644
--- a/src/js/html-filtering.js
+++ b/src/js/html-filtering.js
@@ -50,14 +50,10 @@
             }
             this.needle = new RegExp(arg0, arg1);
         }
-        exec(input) {
-            const output = [];
-            for ( const node of input ) {
-                if ( this.needle.test(node.textContent) ) {
-                    output.push(node);
-                }
+        transpose(node, output) {
+            if ( this.needle.test(node.textContent) ) {
+                output.push(node);
             }
-            return output;
         }
     };
 
@@ -65,14 +61,10 @@
         constructor(task) {
             this.pselector = new PSelector(task[1]);
         }
-        exec(input) {
-            const output = [];
-            for ( const node of input ) {
-                if ( this.pselector.test(node) === this.target ) {
-                    output.push(node);
-                }
+        transpose(node, output) {
+            if ( this.pselector.test(node) === this.target ) {
+                output.push(node);
             }
-            return output;
         }
         get invalid() {
             return this.pselector.invalid;
@@ -81,24 +73,17 @@
     PSelectorIfTask.prototype.target = true;
 
     const PSelectorIfNotTask = class extends PSelectorIfTask {
-        constructor(task) {
-            super(task);
-            this.target = false;
-        }
     };
+    PSelectorIfNotTask.prototype.target = false;
 
     const PSelectorMinTextLengthTask = class {
         constructor(task) {
             this.min = task[1];
         }
-        exec(input) {
-            const output = [];
-            for ( const node of input ) {
-                if ( node.textContent.length >= this.min ) {
-                    output.push(node);
-                }
+        transpose(node, output) {
+            if ( node.textContent.length >= this.min ) {
+                output.push(node);
             }
-            return output;
         }
     };
 
@@ -106,20 +91,37 @@
         constructor(task) {
             this.nth = task[1];
         }
-        exec(input) {
-            const output = [];
-            for ( let node of input ) {
-                let nth = this.nth;
-                for (;;) {
-                    node = node.parentElement;
-                    if ( node === null ) { break; }
-                    nth -= 1;
-                    if ( nth !== 0 ) { continue; }
-                    output.push(node);
-                    break;
-                }
+        transpose(node, output) {
+            let nth = this.nth;
+            for (;;) {
+                node = node.parentElement;
+                if ( node === null ) { return; }
+                nth -= 1;
+                if ( nth === 0 ) { break; }
+            }
+            output.push(node);
+        }
+    };
+
+    const PSelectorSpathTask = class {
+        constructor(task) {
+            this.spath = task[1];
+        }
+        transpose(node, output) {
+            const parent = node.parentElement;
+            if ( parent === null ) { return; }
+            let pos = 1;
+            for (;;) {
+                node = node.previousElementSibling;
+                if ( node === null ) { break; }
+                pos += 1;
+            }
+            const nodes = parent.querySelectorAll(
+                `:scope > :nth-child(${pos})${this.spath}`
+            );
+            for ( const node of nodes ) {
+                output.push(node);
             }
-            return output;
         }
     };
 
@@ -127,25 +129,21 @@
         constructor(task) {
             this.xpe = task[1];
         }
-        exec(input) {
-            const output = [];
-            const xpe = docRegister.createExpression(this.xpe, null);
-            let xpr = null;
-            for ( const node of input ) {
-                xpr = xpe.evaluate(
-                    node,
-                    XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,
-                    xpr
-                );
-                let j = xpr.snapshotLength;
-                while ( j-- ) {
-                    const node = xpr.snapshotItem(j);
-                    if ( node.nodeType === 1 ) {
-                        output.push(node);
-                    }
+        transpose(node, output) {
+            const xpr = docRegister.evaluate(
+                this.xpe,
+                node,
+                null,
+                XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE,
+                null
+            );
+            let j = xpr.snapshotLength;
+            while ( j-- ) {
+                const node = xpr.snapshotItem(j);
+                if ( node.nodeType === 1 ) {
+                    output.push(node);
                 }
             }
-            return output;
         }
     };
 
@@ -181,22 +179,28 @@
             let nodes = this.prime(input);
             for ( const task of this.tasks ) {
                 if ( nodes.length === 0 ) { break; }
-                nodes = task.exec(nodes);
+                const transposed = [];
+                for ( const node of nodes ) {
+                    task.transpose(node, transposed);
+                }
+                nodes = transposed;
             }
             return nodes;
         }
         test(input) {
             if ( this.invalid ) { return false; }
             const nodes = this.prime(input);
-            const AA = [ null ];
             for ( const node of nodes ) {
-                AA[0] = node;
-                let aa = AA;
+                let output = [ node ];
                 for ( const task of this.tasks ) {
-                    aa = task.exec(aa);
-                    if ( aa.length === 0 ) { break; }
+                    const transposed = [];
+                    for ( const node of output ) {
+                        task.transpose(node, transposed);
+                    }
+                    output = transposed;
+                    if ( output.length === 0 ) { break; }
                 }
-                if ( aa.length !== 0 ) { return true; }
+                if ( output.length !== 0 ) { return true; }
             }
             return false;
         }
@@ -209,7 +213,8 @@
         [ ':min-text-length', PSelectorMinTextLengthTask ],
         [ ':not', PSelectorIfNotTask ],
         [ ':nth-ancestor', PSelectorNthAncestorTask ],
-        [ ':xpath', PSelectorXpathTask ]
+        [ ':spath', PSelectorSpathTask ],
+        [ ':xpath', PSelectorXpathTask ],
     ]);
     PSelector.prototype.invalid = false;
 
diff --git a/src/js/static-ext-filtering.js b/src/js/static-ext-filtering.js
index b9d4c873e..e8a795d9d 100644
--- a/src/js/static-ext-filtering.js
+++ b/src/js/static-ext-filtering.js
@@ -169,6 +169,7 @@
                 'min-text-length',
                 'not',
                 'nth-ancestor',
+                'watch-attr',
                 'watch-attrs',
                 'xpath'
                 ].join('|'),
@@ -285,6 +286,7 @@
             [ ':-abp-contains', ':has-text' ],
             [ ':-abp-has', ':has' ],
             [ ':contains', ':has-text' ],
+            [ ':watch-attrs', ':watch-attr' ],
         ]);
 
         const compileArgument = new Map([
@@ -299,7 +301,7 @@
             [ ':not', compileNotSelector ],
             [ ':nth-ancestor', compileNthAncestorSelector ],
             [ ':spath', compileSpathExpression ],
-            [ ':watch-attrs', compileAttrList ],
+            [ ':watch-attr', compileAttrList ],
             [ ':xpath', compileXpathExpression ]
         ]);
 
@@ -356,7 +358,7 @@
                     break;
                 case ':min-text-length':
                 case ':nth-ancestor':
-                case ':watch-attrs':
+                case ':watch-attr':
                 case ':xpath':
                     raw.push(`${task[0]}(${task[1]})`);
                     break;